Revise breaking change note and add validation info

Updated breaking change note formatting and added validation details.

Author: mfranzke

.changeset/brown-falcons-melt.md

@@ -7,6 +7,6 @@
 ---
 
 feat: Switch stable rework
-BREAKING CHANGE: remove `emphasis` property
+**BREAKING CHANGE**: remove `emphasis` property
 introduce validation (invalid and valid)
 configurable label position