When uploading multiple emoji in Admin/Customize/Emojis with an emoji Group selected, the group was cleared between each file uploaded, making bulk uploading of emojis a chore if anything but the default group was needed.
This commit fixes the issue, introduces tests for emoji-uploader,
and also adds
add-files appEvents for uppy-upload mixin, same
as the composer-upload-uppy mixin, for interop with tests and so
we don’t have to rely on a file upload element’s change event.