No way to add back in main.blocks

[jwunderl]

Describe the bug

if you accidentally delete main.blocks, there's no easy to bring it back. I would expect adding main.blocks as a custom file would bring it back

To Reproduce
Steps to reproduce the behavior:

1. Go to https://arcade.makecode.com/S50476-03517-73092-94476
2. can't make main.blocks come back up

Expected behavior
If the user adds a new file called 'main.blocks', and 'main.ts' exists, I would expect it to decompile main.ts back and make it a blocks project again. if main.ts does not exist, I would expect it to create both files as empty files / maybe just on start

Additional context

User having trouble with it here https://forum.makecode.com/t/i-accidentally-deleted-main-blocks/19271/2, I'll probably just manually fix their project but it'd be good to have a general solution.