Codesandbox-client: .jsx file extension support

[CompuIves]

This one should be easy to do, I found out that create-react-app does support the jsx extension. We should update the sandbox to handle these cases.

All the code for this resides in src/sandbox/, if you'd search for js you'll find where we check for the extension.

I believe all logic is in src/sandbox/eval/js/index.js and src/sandbox/utils/resolve-module.js.

[bengummer]

Hey @CompuIves I am keen to have a go at this issue in the next week or so. Been wanting to get to know the codebase so this seems like a good starting point.

P.S. I was initially confused by the issue title, thought it meant JSX support in the editor rather than filenames. Maybe "JSX file extension support"? No big deal either way :)

[CompuIves]

That's really great @bengummer! I updated the title, don't hesitate to message me if you have any questions 😄 .