Highlight Asciidoc as plaintext

doc/user/asciidoc.md

@@ -10,14 +10,14 @@ You can find the full documentation for the AsciiDoc syntax at <https://asciidoc
 
 ### Paragraphs
 
-```asciidoc
+```plaintext
 A normal paragraph.
 Line breaks are not preserved.
 ```
 
 Line comments, which are lines that start with `//`, are skipped:
 
-```asciidoc
+```plaintext
 // this is a comment
 ```
 
@@ -25,7 +25,7 @@ A blank line separates paragraphs.
 
 A paragraph with the `[%hardbreaks]` option will preserve line breaks:
 
-```asciidoc
+```plaintext
 [%hardbreaks]
 This paragraph carries the `hardbreaks` option.
 Notice how line breaks are now preserved.
@@ -35,7 +35,7 @@ An indented (literal) paragraph disables text formatting,
 preserves spaces and line breaks, and is displayed in a
 monospaced font:
 
-```asciidoc
+```plaintext
  This literal paragraph is indented with one space.
  As a consequence, *text formatting*, spaces,
  and lines breaks will be preserved.
@@ -43,7 +43,7 @@ monospaced font:
 
 An admonition paragraph grabs the reader's attention:
 
-```asciidoc
+```plaintext
 NOTE: This is a brief reference, please read the full documentation at https://asciidoctor.org/docs/.
 
 TIP: Lists can be indented. Leading whitespace is not significant.
@@ -53,7 +53,7 @@ TIP: Lists can be indented. Leading whitespace is not significant.
 
 **Constrained (applied at word boundaries)**
 
-```asciidoc
+```plaintext
 *strong importance* (aka bold)
 _stress emphasis_ (aka italic)
 `monospaced` (aka typewriter text)
@@ -64,7 +64,7 @@ _stress emphasis_ (aka italic)
 
 **Unconstrained (applied anywhere)**
 
-```asciidoc
+```plaintext
 **C**reate+**R**ead+**U**pdate+**D**elete
 fan__freakin__tastic
 ``mono``culture
@@ -72,7 +72,7 @@ fan__freakin__tastic
 
 **Replacements**
 
-```asciidoc
+```plaintext
 A long time ago in a galaxy far, far away...
 (C) 1976 Arty Artisan
 I believe I shall--no, actually I won't.
@@ -80,7 +80,7 @@ I believe I shall--no, actually I won't.
 
 **Macros**
 
-```asciidoc
+```plaintext
 // where c=specialchars, q=quotes, a=attributes, r=replacements, m=macros, p=post_replacements, etc.
 The European icon:flag[role=blue] is blue & contains pass:[************] arranged in a icon:circle-o[role=yellow].
 The pass:c[->] operator is often referred to as the stabby lambda.
@@ -93,12 +93,12 @@ stem:[sqrt(4) = 2]
 
 **User-defined attributes**
 
-```asciidoc
+```plaintext
 // define attributes in the document header
 :name: value
 ```
 
-```asciidoc
+```plaintext
 :url-gem: https://rubygems.org/gems/asciidoctor
 
 You can download and install Asciidoctor {asciidoctor-version} from {url-gem}.
@@ -117,7 +117,7 @@ GitLab sets the following environment attributes:
 
 ### Links
 
-```asciidoc
+```plaintext
 https://example.org/page[A webpage]
 link:../path/to/file.txt[A local file]
 xref:document.adoc[A sibling document]
@@ -126,7 +126,7 @@ mailto:hello@example.org[Email to say hello!]
 
 ### Anchors
 
-```asciidoc
+```plaintext
 [[idname,reference text]]
 // or written using normal block attributes as `[#idname,reftext=reference text]`
 A paragraph (or any block) with an anchor (aka ID) and reftext.
@@ -142,7 +142,7 @@ This paragraph has a footnote.footnote:[This is the text of the footnote.]
 
 #### Unordered
 
-```asciidoc
+```plaintext
 * level 1
 ** level 2
 *** level 3
@@ -161,7 +161,7 @@ Attach a block or paragraph to a list item using a list continuation (which you
 
 #### Ordered
 
-```asciidoc
+```plaintext
 . Step 1
 . Step 2
 .. Step 2a
@@ -177,14 +177,14 @@ Attach a block or paragraph to a list item using a list continuation (which you
 
 #### Checklist
 
-```asciidoc
+```plaintext
 * [x] checked
 * [ ] not checked
 ```
 
 #### Callout
 
-```asciidoc
+```plaintext
 // enable callout bubbles by adding `:icons: font` to the document header
 [,ruby]
 ----
@@ -195,7 +195,7 @@ puts 'Hello, World!' # <1>
 
 #### Description
 
-```asciidoc
+```plaintext
 first term:: description of first term
 second term::
 description of second term
@@ -205,7 +205,7 @@ description of second term
 
 #### Header
 
-```asciidoc
+```plaintext
 = Document Title
 Author Name <author@example.org>
 v1.0, 2019-01-01
@@ -213,7 +213,7 @@ v1.0, 2019-01-01
 
 #### Sections
 
-```asciidoc
+```plaintext
 = Document Title (Level 0)
 == Level 1
 === Level 2
@@ -225,7 +225,7 @@ v1.0, 2019-01-01
 
 #### Includes
 
-```asciidoc
+```plaintext
 include::basics.adoc[]
 
 // define -a allow-uri-read to allow content to be read from URI
@@ -239,13 +239,13 @@ included, a number that is inclusive of transitive dependencies.
 
 ### Blocks
 
-```asciidoc
+```plaintext
 --
 open - a general-purpose content wrapper; useful for enclosing content to attach to a list item
 --
 ```
 
-```asciidoc
+```plaintext
 // recognized types include CAUTION, IMPORTANT, NOTE, TIP, and WARNING
 // enable admonition icons by setting `:icons: font` in the document header
 [NOTE]
@@ -254,13 +254,13 @@ admonition - a notice for the reader, ranging in severity from a tip to an alert
 ====
 ```
 
-```asciidoc
+```plaintext
 ====
 example - a demonstration of the concept being documented
 ====
 ```
 
-```asciidoc
+```plaintext
 .Toggle Me
 [%collapsible]
 ====
@@ -268,58 +268,58 @@ collapsible - these details are revealed by clicking the title
 ====
 ```
 
-```asciidoc
+```plaintext
 ****
 sidebar - auxiliary content that can be read independently of the main content
 ****
 ```
 
-```asciidoc
+```plaintext
 ....
 literal - an exhibit that features program output
 ....
 ```
 
-```asciidoc
+```plaintext
 ----
 listing - an exhibit that features program input, source code, or the contents of a file
 ----
 ```
 
-```asciidoc
+```plaintext
 [,language]
 ----
 source - a listing that is embellished with (colorized) syntax highlighting
 ----
 ```
 
-````asciidoc
+````plaintext
 \```language
 fenced code - a shorthand syntax for the source block
 \```
 ````
 
-```asciidoc
+```plaintext
 [,attribution,citetitle]
 ____
 quote - a quotation or excerpt; attribution with title of source are optional
 ____
 ```
 
-```asciidoc
+```plaintext
 [verse,attribution,citetitle]
 ____
 verse - a literary excerpt, often a poem; attribution with title of source are optional
 ____
 ```
 
-```asciidoc
+```plaintext
 ++++
 pass - content passed directly to the output document; often raw HTML
 ++++
 ```
 
-```asciidoc
+```plaintext
 // activate stem support by adding `:stem:` to the document header
 [stem]
 ++++
@@ -327,7 +327,7 @@ x = y^2
 ++++
 ```
 
-```asciidoc
+```plaintext
 ////
 comment - content which is not included in the output document
 ////
@@ -335,7 +335,7 @@ comment - content which is not included in the output document
 
 ### Tables
 
-```asciidoc
+```plaintext
 .Table Attributes
 [cols=>1h;2d,width=50%,frame=topbot]
 |===
@@ -366,7 +366,7 @@ comment - content which is not included in the output document
 
 ### Multimedia
 
-```asciidoc
+```plaintext
 image::screenshot.png[block image,800,450]
 
 Press image:reload.svg[reload,16,opts=interactive] to reload the page.
@@ -380,12 +380,12 @@ video::300817511[vimeo]
 
 ### Breaks
 
-```asciidoc
+```plaintext
 // thematic break (aka horizontal rule)
 ---
 ```
 
-```asciidoc
+```plaintext
 // page break
 <<<
 ```