* Update selectors for button blocks, for better custom colour fallbacks.
* Update drop cap size, to scale when font size does.
* Add visited states to custom colours.
* Position bullets inside of lists when widget blocks are centred.
* Reorganize styles a bit, consolidate header styles, and delete empty selectors
* Update editor colour palette to match theme's colours
* Remove styles for pre and code blocks in editor; doesn't look identical to the front-end but they blocked the text from being edited
