Put our CSS variables in `assets` instead of `static`

[choldgraf]

Context

There are two places where we currently define CSS variables:

• We define a bunch of UI variables in static/ here: https://github.com/pydata/pydata-sphinx-theme/blob/master/src/pydata_sphinx_theme/theme/pydata_sphinx_theme/static/styles/theme.css
• We define a bunch of color-related variables in base/ here: https://github.com/pydata/pydata-sphinx-theme/blob/master/src/pydata_sphinx_theme/assets/styles/base/_color.scss

We also have:

• An abstract/ folder here: https://github.com/pydata/pydata-sphinx-theme/tree/master/src/pydata_sphinx_theme/assets/styles/abstracts

Proposal

We should move the variables that are in static/ to instead by in a abstract/variables.scss file. I think that this would make it easier to track where our variables are, and have them unified in a single place.

[12rambau]

how is it related to JavaScript ? I only see .scss files here (but maybe you're referring to the way it's build

[choldgraf]

Oops it should say CSS not JavaScript 🤦 changing now!