@uppy/core: migrate to TS

[Murderlon]

Most noteworthy is that the Uppy class now takes two generics:

 export class Uppy<M extends Meta, B extends Body>

This is so we can correctly type Uppy files with custom metadata and the response body from uploaders.

export interface UppyFile<M extends Meta, B extends Body> {
  // ...
  meta: InternalMetadata & M
  response?: {
    body: B
    status: number
    bytesUploaded?: number
    uploadURL: string
  }
}

In the case of xhr-upload the body is something people have to type themselves because it's their own backend. When working with tus or Transloadit, I imagine we probably need to do something like this:

import type { Response } from '@uppy/transloadit'

type MyMeta = { foo: number }

new Uppy<MyMeta, Response>()

[aduh95]

I guess that's what causing production TS to ignore untyped dependencies, and because it's not present in tsconfig.json, it reports an error. Maybe we want to re-enable it on prod (and have @ts-expect-error in source files), or we'd want to skip it on the shared options

[arturi]

Why three ons?

[aduh95]

One is deprecated

[kvz]

Congrats on landing this team! Milestone! ✨✨💖✨

[arturi]

Massive effort by @Murderlon and @aduh95 (initial TS build setup, utils)!