Prepare project's JSON for extension

[0832k12]

Proposed Changes

Changed the deserializeProject method in virtual-machine.js to allow extensions to read the project's JSON when loaded with the project.

Reason for Changes

Used to obtain the complete project JSON when the extension is loaded for use by the extension and expand the functionality of the extension.

Test Coverage

[yuri-kiss]

i just noticed, this runs before serialization, does that mean we can use it for storage in the project?

[GarboMuffin]

if this was for storage then it was superseded by https://github.com/TurboWarp/scratch-vm/pull/179