Related commits:
- 0662767dd6
- 99b2a0a761
- a8e3118fea
- 453f5450b6
- a45a21f337
This commit focuses on implementing the use of
CSS `var(...)` throughout so as to make it easy
to create themes -- a requirement for uBO to
support a dark theme.
There is still work to do regarding converting
uBO's CSS to completely support `var(...)` but
being able to start using theming will help
complete and fine tune CSS `var(...)` support.
Related issue:
- https://github.com/uBlockOrigin/uBlock-issues/issues/401
