Expose @uppy/drop-target events

[Murderlon]

Supersedes #2973

Alternative approach to make the solution more generic and aligned with previous solutions.

• Expose events
• Update types
• Update docs

---

The problem @tobiasps posed could now be solved like so (in combination with uppy.setFileMeta)

    .use(DropTarget, {
      // ...
      onDrop: (event) => {
        const { files } = uppyInstance.getState()
        // do something with `event` and `files`
      }),
    })

[aduh95]

Should we pass the files here?

Suggested change

	this.opts.onDrop?.(event)
	this.opts.onDrop?.(event, files)

[Murderlon]

I thought about it but I didn't in the end.

• It's inconsistent with what we pass in the other events in this plugin, but also with the events in other plugins
• files here is not the same as this.uppy.getState().files, it is not processed yet so it missing important things like id.
• the idea of these events is that it can be used for any side effect, so the developer can access whatever they want from the uppy instance should they need it

[arturi]

Ok, good point about these being unprocessed files especially.