Add Bikeshed support

[kfranqueiro]

This adds support to spec-generator for generating Bikeshed specs and issue lists, in a way that provides near-parity with the features of the CSSWG API.

Functionality included:

• Setting what event level to die on (via HTML form or die-on)
• Overriding the date in specs (via HTML form or md-date)
• Setting the Prepare for TR flag (via HTML form or md-prepare-for-tr)
• Arbitrary metadata overrides (via md-<key>)
• Specifying a URL or uploading a standalone or tar file for both specs and issue lists
  • This is particularly notable for the case of issue list URLs, as the CLI and CSSWG API do not support this
• Expandable help section with details on the HTTP API

The most notable thing that isn't included is an equivalent to the CSSWG API's output=err, which I'd like to work on separately after this, to avoid making this PR even bigger.

The diff will be rather large, because I moved the majority of the code that had been in server.ts into generator/respec.ts in the process, as a lot of it was respec-specific. Now generator/bikeshed.ts and generator/respec.ts each export a similar API which server.ts calls after validating parameters, depending on the type parameter.

Other changes included in this PR:

• Carries over die-on support to ReSpec, to maximize the amount of shared fields between the available generators
• Carries over md-date and md-<key> support to ReSpec, to make it possible to override respecConfig properties even in case of file upload, which previously wasn't possible
• Makes start function in server.ts async, to wait until the server is listening
• Reformats all TS files and index.html to 2-space indent (from 4) to match other repos and default Prettier settings; since this PR results in a lot of changed lines already due to most code being added or relocated, it made sense to tackle this now as well (already discussed with Denis)
  • Note: I tried running index.html through Prettier in the process, but ended up re-excluding it because of a couple of non-configurable decisions Prettier makes that I disagree with, primarily the inclusion of self-closing tags
  • Also note this means that hiding whitespace in the PR diff will make it at least a little bit less noisy
• Updates npm run watch to also restart on HTML changes
• Updates npm test to correctly run all tests - and there are many more now, including tests across GET, POST, and POST with query string parameters, wherever applicable
• Updates test workflow to use ubuntu-latest in order to get Python >= 3.12 for use with Bikeshed 7, which further required adding a command to enable puppeteer to continue to work for ReSpec tests

[sidvishnoi]

Small enhancement: If url parameter has ?type set, we can check the right radio buttons with script.

[kfranqueiro]

Is there a use case for this enhancement? I ask because this would expose multiple edge cases if the user were to change the Document type choice after loading this way:

• Doing this client-side would override any previous user input within these radio buttons if the user were to refresh the page or revisit the form via browser history
  • Doing this server-side would avoid this, but would involve adding more complexity and dependencies to the Express setup (which I had considered doing earlier in this PR, but later decided to avoid when merging back to a single page)
• GET parameters currently override POST parameters if both are present; I'd need to flip this, otherwise the form submission (which uses action="" to work regardless of base path) will break if a user changes the Document type, then performs a file upload with type in the URL
  • Changing this might be fine; many curl use cases found across GitHub use GET parameters with a POST request, but are unlikely to define the same parameter both ways

[sidvishnoi]

I'm open to skipping it as it was a small potential improvement, considering the concerns raised.