Remove reliance on `polymer-cli`

[jkomoros]

PWA starter kit example with WebPack: https://github.com/Polymer/pwa-starter-kit/tree/webpack

LitElement https://lit.dev/docs/v1/tools/build/#build-requirements

Blocks #528.

[jkomoros]

• [x] before committing verify that the old service worker doesn't mess with this one
• [x] Update service-worker generation: https://developer.chrome.com/docs/workbox/migration/migrate-from-sw/
• [x] Verify service-worker from old to do new works in deploy
• [x] Make sure screenshot service works
• [x] Clear build dir when building: https://www.npmjs.com/package/rollup-plugin-cleaner
• [x] Remove all mentions of polymer in gulpfile.js variables and messages
• [x] Verify tests all run
• [x] Fix circular dependencies warnings
• [x] Fix minify-html-literals warnings
• [ ] Install lit-plugin on mac pro (see #590)
• [x] Remove references to polymer in README
• [x] Remove polymer.json
• [x] Re-enable service worker generation
• [x] Use https://modern-web.dev/docs/building/rollup-plugin-html/ on the index.html directly
• [x] Why is there a no-op import from card-web-app.js to one with a nonce? Won't that lead to extra round-trips in production? That's a facade export because https://rollupjs.org/guide/en/#preserveentrysignatures is set to 'strict'. Being able to use rollup-plugin-html (which apparently skips type=module imports?) would allow this to be set to false.
• [ ] Inspect imports to see which ones are most expensive
• [x] Figure out a way to cut out extraneous/duplicated comments in build output
• [x] Remove gulp prpl-server

[jkomoros]

Being developed in branch rollup-build

[jkomoros]

Verified service-worker from old to new works in a production deploy.