support importing css into lit components, clean up rspack loaders

[LeoMcA]

Adds import styles from "./foobar.css?lit" which wraps the contents of foobar.css with the lit css template tag.

Not using https://developer.mozilla.org/en-US/docs/Web/API/CSSStyleSheet/CSSStyleSheet as it's baseline blue, and not supported in node. Not using the language feature formerly known as import assertions because typescript doesn't have support for it (for writing our module definitions).

Also changes import svg from "./foobar.svg?mdnsvg" to import svg from "./foobar.svg?lit" for consistency.

Adds support for importing svgs and getting a path to the asset location like import path from "./foobar.svg"

[github-actions]

f8bca4d was deployed to: https://fred-pr29.review.mdn.allizom.net/