feat: introduce a build step

[florian-lefebvre]

Closes #54, closes #78, closes #50, closes #85.

TODO:

• [x] Have build working (requires dts to work for all utilities and plugins)
• [x] Test
• [x] Update release script
• [x] Update contribution guide (readme)
• [x] Update breaking changes docs
• [x] Update tsup to exclude ambient.d.ts specifically
• [x] Add github action that builds on prs
• [ ] Hot reloading (help wanted!)

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