Uploading large files

[robertutterback]

Uploading small files is no problem, but we will probably need changes to handle large files.

1. Compress them?
2. Use streaming so they don't all have to be buffered at once. I'm
   think Sveltekit is still working on some things in this area.
3. Do we need to submit files separately? Does it help? It does
   actually help with having separate progress bars for each file,
   which is kind of nice.