Add guidance to avoid semicolons

doc/development/documentation/styleguide/index.md

@@ -601,6 +601,7 @@ Follow these guidelines for punctuation:
 
 | Rule                                                             | Example                                                |
 |------------------------------------------------------------------|--------------------------------------------------------|
+| Avoid semicolons. Use two sentences instead.                     | _That's the way that the world goes 'round. You're up one day and the next you're down._
 | Always end full sentences with a period.                         | _For a complete overview, read through this document._ |
 | Always add a space after a period when beginning a new sentence. | _For a complete overview, check this doc. For other references, check out this guide._ |
 | Do not use double spaces. (Tested in [`SentenceSpacing.yml`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/doc/.vale/gitlab/SentenceSpacing.yml).) | --- |