fix: CSS Syntax Error

[mxkae]

fixes #3087

[github-actions]

🤖 Pull request artifacts

file	commit
pr3198-stackable-3198-merge.zip	9ea23b7

[github-actions]

Try this Pull Request in the WordPress playground: https://playground.wordpress.net/?mode=seamless#{"landingPage":"/wp-admin/post-new.php?post_type=page","preferredVersions":{"php":"latest","wp":"latest"},"steps":[{"step":"login","username":"admin","password":"password"},{"step":"installPlugin","pluginZipFile":{"resource":"url","url":"https://raw.githubusercontent.com/gambitph/Stackable/artifacts/pr3198-stackable-3198-merge.zip"}}]}

[mxkae]

Added some documentation and notes for this fix: https://www.notion.so/Fix-3087-CSS-Syntax-Error-51ac4321311d4a1e8d1a673b422fc6cb

[bfintal]

@andeng1106 the QA here is that the affected code and blocks should still have the correct styling after the fixes are applied. Also, the yellow labs testing should also have errors fixed