Add version mermaid support was introduced

doc/user/markdown.md

@@ -41,7 +41,7 @@ Line-breaks, or softreturns, are rendered if you end a line with two or more spa
 
     Sugar is sweet
 
-Roses are red  
+Roses are red
 Violets are blue
 
 Sugar is sweet
@@ -370,14 +370,17 @@ This also works for the asciidoctor `:stem: latexmath`. For details see the [asc
 
 ### Mermaid
 
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/15107) in
+GitLab 10.3.
+
 > If this is not rendered correctly, see
 https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/user/markdown.md#mermaid
 
-It is possible to generate diagrams and flowcharts from text using [Mermaid][mermaid]. 
+It is possible to generate diagrams and flowcharts from text using [Mermaid][mermaid].
 
-In order to generate a diagram or flowchart, you should write your text inside the `mermaid` block. 
+In order to generate a diagram or flowchart, you should write your text inside the `mermaid` block.
 
-Example: 
+Example:
 
     ```mermaid
     graph TD;
@@ -385,7 +388,7 @@ Example:
       A-->C;
       B-->D;
       C-->D;
-    ```   
+    ```
 
 Becomes:
 
@@ -395,7 +398,7 @@ graph TD;
   A-->C;
   B-->D;
   C-->D;
-```   
+```
 
 For details see the [Mermaid official page][mermaid].
 
@@ -697,7 +700,7 @@ This line is separated from the one above by two newlines, so it will be a *sepa
 This line is also a separate paragraph, but...
 This line is only separated by a single newline, so it *does not break* and just follows the previous line in the *same paragraph*.
 
-This line is also a separate paragraph, and...  
+This line is also a separate paragraph, and...
 This line is *on its own line*, because the previous line ends with two spaces. (but still in the *same paragraph*)
 
 spaces.
@@ -710,7 +713,7 @@ This line is separated from the one above by two newlines, so it will be a *sepa
 This line is also a separate paragraph, but...
 This line is only separated by a single newline, so it *does not break* and just follows the previous line in the *same paragraph*.
 
-This line is also a separate paragraph, and...  
+This line is also a separate paragraph, and...
 This line is *on its own line*, because the previous line ends with two spaces. (but still in the *same paragraph*)
 
 spaces.