Add guidelines for fixing spelling mistakes

doc/development/documentation/testing.md

@@ -210,6 +210,20 @@ Vale returns three types of results: `suggestion`, `warning`, and `error`:
   of how to resolve the error. Errors break CI and are displayed in CI job output. See a list of
   [error-level rules](https://gitlab.com/search?utf8=✓&snippets=false&scope=&repository_ref=master&search=path%3Adoc%2F.vale%2Fgitlab+Error%3A&group_id=9970&project_id=278964).
 
+#### Vale spelling test
+
+When Vale flags a valid word as a spelling mistake, you can fix it following these
+guidelines:
+
+| Flagged word                                         | Guideline |
+|------------------------------------------------------|-----------|
+| jargon                                               | Rewrite the sentence to avoid it. |
+| *correctly-capitalized* name of a product or service | Add the word to the [vale spelling exceptions list](https://gitlab.com/gitlab-org/gitlab/-/blob/master/doc/.vale/gitlab/spelling-exceptions.txt). |
+| name of a person                                     | Remove the name if it's not needed, or [add the vale exception code in-line](#disable-vale-tests). |
+| a command, variable, code, or similar                | Put it in backticks or a code block. For example: ``The git clone command can be used with the CI_COMMIT_BRANCH variable.`` -> ``The `git clone` command can be used with the `CI_COMMIT_BRANCH` variable.`` |
+| UI text from GitLab                                  | Verify it correctly matches the UI, then: <ul><li>If it does not match the UI, update it.</li><li>If it matches the UI, but the UI seems incorrect, create an issue to see if the UI needs to be fixed.</li><li>If it matches the UI and seems correct, add it to the [vale spelling exceptions list](https://gitlab.com/gitlab-org/gitlab/-/blob/master/doc/.vale/gitlab/spelling-exceptions.txt).</li></ul> |
+| UI text from a third-party product                   | Rewrite the sentence to avoid it, or [add the vale exception code in-line](#disable-vale-tests). |
+
 ### Install linters
 
 At a minimum, install [markdownlint](#markdownlint) and [Vale](#vale) to match the checks run in