4.x launch

[kvz]

TODO

• TypeScript port (already in main)
• Remove isResumable (always use tus) (@mifi) remove isResumable option #209
• Add Loose just strict Robot schemas/types so consuming devs have autocomplete for Assembly Instructions when they use the Node SDK without TypeScript erroring out if they use a new FFmpeg stack version that their types didn’t know about yet (@remcohaszing)
• Add better errors (may mean vendoring Got? Do whatever is easiest & safe that will get us better errors. We'll revise this in 5.x most likely) (@mifi)
• Get an RC out to test the experience on the consuming side (upgrade content repo with it, etc) (@remcohaszing)
• Add changesets for auto releases (@remcohaszing)
• Final kinks (@remcohaszing)
• Release 4.0 (@remcohaszing)
• Ping @Acconut, he wants to use the Smart CDN sig auth that is now also released (@remcohaszing)

We're saving these for 5.x. Explicitly not doing:

• ESM port (unless we do dual exports; so to CJS as well)
• Handle progress for all the runtimes in tus-js-client, so we can then:
• Release multi-runtime support (edge, deno, browser, node, etc) (or @transloadit/client)