This PR adds uppy to the project with a custom JS build and the shims needed to import it into our JS code. We need a custom build of Uppy because we do not use webpack for our JS modules/build. The only way to get what you want from Uppy is to use the webpack modules or to include the entire Uppy project including all plugins in a single JS file. This way we can just use the plugins we actually want. Future PRs will actually use Uppy!
