Fix react-refresh source maps

[soxtoby]

Resolves #12483

The react-router:react-refresh-babel transform was wrapping the code with big chunks of code that completely threw off the source maps. I've changed the wrapping code to use babel to maintain the source maps, and split it off into a new transform step so the source maps from the previous transform flow through.

[remorses]

I propose another solution: put the react refresh header in a single line, then remove the first new line of the file. This way only the first line sourcemaps will be wrong, which shouldn’t matter anyway because it only contains imports.

this technique is already used by Vite for other transformations, it lets you skip parsing one more time with Babel which is expensive

[changeset-bot]

🦋 Changeset detected

Latest commit: b35ddb1

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

This PR includes changesets to release 11 packages

Name	Type
@react-router/dev	Patch
@react-router/fs-routes	Patch
@react-router/remix-routes-option-adapter	Patch
create-react-router	Patch
react-router	Patch
react-router-dom	Patch
@react-router/architect	Patch
@react-router/cloudflare	Patch
@react-router/express	Patch
@react-router/node	Patch
@react-router/serve	Patch

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[remix-cla-bot]

Thank you for signing the Contributor License Agreement. Let's get this merged! 🥳

[soxtoby]

@remorses thanks for suggestion - the output isn't as pretty, but the code is much simpler, and the source maps are even better since the first line of code comes from react-refresh and was already unmapped.

[markdalgleish]

I've run this locally and confirmed it works. Thanks for the PR 🙏

[github-actions]

🤖 Hello there,

We just published version 7.1.2-pre.0 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

Thanks!