We should support Cloudflare R2 as a backend in the file-storage package.

We can probably support this using R2's S3 compatibility API. It looks like it has all the features we need and it won't cost us anything in terms of performance. This also means that we can probably use aws4fetch internally and have a common dep with the AWS S3 file-storage adapter.

This API should be available under the @remix-run/file-storage/r2 export.