* quick fix for incorrect arbitrary properties
Turns out that using links like [https://example.com] causes arbitrary
properties to generate invalid css.
This is a very dirty quick fix for this specific case, so we have to fix
this properly!
* update changelog
* Basic implementation + some failing tests for edge cases
* Use asClass instead of nameClass
* Solve edge cases around content with colons
* Avoid duplicating work when parsing arbitrary properties
* Update changelog