RemixSite ESM support

[sockthedev]

Work in progress

This is my effort to get Remix working nicely in SST "drop in" mode. I'm attempting to get the Remix project running and outputting ESM, with the hope of support SST bind.

Current changes represented by PR:

• Move the validation of the Remix configuration into a separate process.

  Prior to this we were using a require statement which was breaking the build when I tried to toggle my Remix project into ESM mode via the package.json "type": "module" setting.

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: eaf6f7967f30286330130c6cc1fd7f2c02802441

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[fwang]

Implemented in #3303