docs(style guide): one sentence per line, no punctuation at end of list item (#23660)

docs/development/style-guide.md

@@ -10,6 +10,26 @@ This document describes the correct style for user-facing text in the:
 
 Set your spell checker to the correct language.
 
+## One sentence per line
+
+In Markdown files, use one sentence per line.
+Like this:
+
+```markdown
+First sentence on one line.
+Second sentence on a new line.
+And so on.
+```
+
+## Avoid punctuation at the end of list items
+
+In Markdown files, avoid punctuation at the end of a list item.
+Like this:
+
+```markdown
+- List item, no punctuation at the end
+```
+
 ## Use plain language
 
 Follow the [Plain language guidelines](https://www.plainlanguage.gov/guidelines/).