New plan for CSS

[calebeby]

I would like to remove the dependency on rollup-plugin-postcss, it has a very big dependency tree and is not very maintained.

What we need from a CSS solution:

• Import rewriting needs to work
• Don't run postcss or anything by default, so it is as fast as possible
• Allow using sass, scss, stylus, less (user has to install them)
• Minimize maintenance burden
• Postcss needs to work (user has to install it)
• Postcss with CSS modules needs to work - this has to integrate with the JS pipeline
• Need to be able to configure any/all transformers, and add additional ones (maybe sass, scss, stylus, less could be something you have to add 1-5 lines of code to enable)

Nice-to-have:

• Resolving from node_modules
• Caching

[calebeby]

This will be a breaking change