Build reproducibility: pull fonts from npm

We switched from CDNs to serving typefaces as static assets. When a new version of the font is released, this requires the manual step of pulling fonts builds from their upstream websites, clean up unrelated variants, remove them from their entrypoint CSS (e.g. inter.css) and commit the changed files.

This could be automated and made reproducible by switching to a package manager (e.g. npm) to pull the typefaces at build time.

E.g. inter on npm: https://www.npmjs.com/package/inter-ui