[feature request] Rule sets

[SuperMalakan]

A quality of life type update.

Add the ability to add/edit/delete independant editing containers for the css code.

By having the ability to self-contain sets of css it would allow the user to organise the different css projects and user will better know where to go to make modifications instead of scrolling through the entirety of their css code, potentially hundreds of lines, with the possibility of mistakenly removing the wrong line(s) when attempting to remove css.