Add appEntrypoint to @astrojs/react to enable users to wrap every React island with a custom component

[meyer]

Changes

• I added a new option to @astrojs/react, appEntrypoint. It looks a whole lot like the Vue integration’s appEntrypoint option and it functions nearly identically. Specify a path to a file that has a default-exported component and that component will be used to wrap every React island.
• I added Astro.locals to the render context and am passing Astro.locals through to appEntrypoint’s component as a prop called locals. The prop is only set in a server environment; clientside it’s just undefined. Removed for now but you can see the change here (it’s pretty minimal)

Testing

New tests added that cover appEntrypoint in general as well as the locals prop.

Docs

PR with docs update is here: withastro/docs#13208

[changeset-bot]

🦋 Changeset detected

Latest commit: 7783a6c

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

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[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing meyer:meyer/react-wrapper-component (b344880) with main (955edb9)¹}

Summary

✅ 9 untouched benchmarks

Footnotes

1. No successful run was found on main (a29e171) during the generation of this report, so 955edb9 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[matthewp]

Thanks! We're going to discuss this internally and then will get back to you.