Add periods to bullets (#47430)

Author: gewarren

.github/copilot-instructions.md

@@ -24,7 +24,9 @@ Use "might" instead of "may" to indicate possibility. For example, "This method
 
 Use the Oxford comma in lists of three or more items.
 
-Number ordered list items all as "1." instead of "1.", "2.", etc. Use bullets for unordered lists.
+Number ordered list items all as "1." instead of "1.", "2.", etc.
+
+Use bullets for unordered lists. Unless *all* the bullet list items are three words or less, each bullet item should end with a period.
 
 Use **bold** when referring to UI elements. Use `code style` for file names and folders, custom types, and other text that should never be localized.