Revive and rework tooling around exported API

🤔 What's changed?

Upgrade api-extractor to the latest and turn it back on for the api entry point
Also turn it on, with more forgiving configuration, for the root entry point
Fix a bunch of issues (missing exports etc) flagged by api-extractor
Remove api-documenter and the docs it previously generated
Add typedoc and have it deploy to GitHub Pages on every commit to main
Generally improve some documentation and types

⚡️ What's your motivation?

We added api-extractor and api-documenter a while ago for the new /api entry point, but then disabled them due to some weird compatibility issues with hybrid packages and/or protobuf.

As we add more to the /api entry point soon for plugins, and also look to shrink the exports from the root entry point, we'll get a lot of value from api-extractor as it's very good at finding issues that would cause a poor developer experience for consumers. So I wanted to revive this.

api-documenter on the other hand produces output which is not quite so usable/accessible as an HTML site, and it also doesn't handle multiple entry points. typedoc is better suited on both fronts for us. So I wanted to switch to this.

🏷️ What kind of change is this?

:bank: Refactoring/debt/DX (improvement to code design, tooling, documentation etc. without changing behaviour)
:bug: Bug fix (non-breaking change which fixes a defect)

📋 Checklist:

[x] I agree to respect and uphold the Cucumber Community Code of Conduct
[ ] I've changed the behaviour of the code
- [ ] I have added/updated tests to cover my changes.
[x] My change requires a change to the documentation.
- [x] I have updated the documentation accordingly.
[x] Users should know about my change
- [x] I have added an entry to the "Unreleased" section of the CHANGELOG, linking to this pull request.

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cucumber / cucumber-js