Use npm + vite/webpack/whatever to build static files

• use parcel as buildtool for static assets
• use ManifestCacheBuster to find the right hashed assets : https://docs.pylonsproject.org/projects/pyramid/en/latest/narr/assets.html#path-segments-and-choosing-a-cache-buster
• "cache forever" immutable static files : https://whitenoise.readthedocs.io/en/latest/base.html#caching-headers
• document the use of npm + parcel in README
• Dockerize assets pipeline