CSS extraction for webpack apps

[Rich-Harris]

#406, but for webpack

[silentworks]

Is this issue set to address #154?

[Rich-Harris]

Hopefully. I don't really understand what webpack is doing with regards to CSS, and I think it's going to change for webpack 5...

[lukeed]

I was hoping to address this for Svelte + Webpack in general. There's no (easy?) way to do CSS modules with Svelte without the Svelte identifiers.

[jacobmischka]

It seems like this is working for me out of the box for route/chunk styles, but just not for the main.css shared client stylesheet.