feat(storybook-builder): support MDX and autodocs

[bashmish]

What I did

1. integrated MDX
2. improved tests to be able to test both docs and stories (there was a race condition, the solution from the Storybook's own tests partially worked, but I still had an issue and needed to find a way to wait till docs are really rendered, so ended up having a bit more complex waiting logic)
3. autodocs support comes almost for free, but I added tests for it

To make a smooth static build, I rewrite a story import path to have an .mdx.js extension, this also helps with MIME types when in the runtime. Then in the load method of the plugin I convert MDX->JS right away (instead of doing this in transform), so that other plugins get a proper JS in their transform functions.

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: e30da4a0d82ec7fee494b2a55303f57647d17cc6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | ---------------------- | ----- | | @web/storybook-builder | Patch |

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