Add Astro framework handler

[djfarrelly]

Summary

Create an Astro serve handler that uses Astro endpoints.

Notes

• I haven't gotten tests to pass yet, so I wasn't yet able to run my local Astro tests

Checklist

• [x] Added a docs PR that references this PR
• [x] Added unit/integration tests
• [x] Added changesets if applicable

Related

• INN-2485
• inngest/website#614

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: acd04cb7df0ab4037ceab883269af4c9ec0dcff7

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

This PR includes changesets to release 1 package

| Name | Type | | ------- | ----- | | inngest | Minor |

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