Implement background-colour rendering!

Draft background-colour shader.

Integrate backgrounds parsing.

Improve code cleanliness.

Handle initial colour values.

Parse background-colour CSS property.

Integrate colour parsing & add accent-colour support.

accent-colour takes no effort & helps (custom) form controls clash less with webpages.

Add support for transparent, currentcolor, & hsl() colours!

Parse CSS colour hexcodes & keywords.

Start parsing CSS colours!