That’s pretty good, i was just doing something very similar on nostr-editor by exposing a sign function to do exact that
i made a package to make it super easy to upload files to nostr:npub1nxy4qpqnld6kmpphjykvx2lqwvxmuxluddwjamm4nc29ds3elyzsm5avr7. let me know if you have any issues with it.
Discussion
What’s nostr-editor?
A wysiwyg editor to create notes in a nice way, also a content parser for existing notes, but still in the works as I finish media uploads https://github.com/cesardeazevedo/nostr-editor