Actually this is just backported jsx mode for CodeMirror.
A word to the marijnh:
Well, I suppose if three people are working on one, the need for this mode is pressing. And it looks like it's going to be less work to write one myself rather than to keep hinting and reviewing and pushing people in the right direction. You can find my version in b3f9487. Please test it and submit failing test cases. If this helps you in a financial way, a donation to cover the morning spent on this is much appreciated.
This module removes original xml and javascript modes from brackets and replaces it with latest version from CodeMirror. After, jsx file extension is disassociated from javascript mode and new jsx mode is created.
I've created script which fetch xml, javascript and jsx modes from CodeMirror.
Then script concatenate results, wraps result with _header.js and _footer.js and put result into brackets extension main.js.
After everything is done, you'll need to change version in package.json and commit changes.
npm run-script package will produce archive ready to upload.