[App Inventor Open Source Development] Proposal - Multiple Asset File upload

Below is a proposal allowing user to upload multiple asset files.

https://docs.google.com/document/d/1vGXAakoLRNYvfuZXnRqhdQ3t6gix9B5rocKFV8ARn3Y/edit?usp=sharing

Please review and comment.

Hossein, can you please allow comments in the doc?

I would like to suggest that some size limitation checkings are added
to this proposal. If the user is uploading files bigger than certain
size, they should be warned, and if they are actually bigger than the
currently permitted 5MB limit (in total or separately), they should be
stopped.

Sorry, I thought I had it turned on.

Done.

Could this potentially help with https://github.com/mit-cml/appinventor-sources/issues/173 and  https://github.com/mit-cml/appinventor-sources/issues/184 ?