Upgrade scratch blocks so we can use blockly plugins

[pmalacho-mit]

We are wanting to make use of this keyboard navigation blockly plugin as a part of @Samarh18 's research.

Scratch (and specifically scratch-blocks) relies on an older version of blockly that doesn't support plugins.

Luckily, one of the kind folks on the blockly team has made a fork of scratch-blocks, scratch-vm, and scratch-gui to upgrade their blockly version -- nice!

So the work to be done here is:

• enable us to use the blockly team's upgrade -vm -gui and -blocks code
• try out the keyboard navigation plugin (along with other blockly plugins) and see how they behave.

Here is the specific advice of the developer:

https://github.com/gonfunko/scratch-blocks
https://github.com/gonfunko/scratch-gui
https://github.com/gonfunko/scratch-vm

The vast majority of changes are in scratch-blocks, but there are some supporting changes in -gui and -vm as well. You may find it easier to just look at the commits/diffs for those two and apply them to your own, and only sub in scratch-blocks. Scratch's instructions for linking the repos should work fine, although you'll need to make sure you're using the modern-blockly branch of my repos, and ensure that scratch-blocks is also linked to the rc/v12.0.0 branch of core Blockly. You'll probably need the --force flag to npm install as well. I'm happy to help if you get stuck on anything, and excited to hear how it goes!

So I think you should take this approach. Do as they^ say and pinpoint what changes were necessary on -vm and -gui repos, and then apply those changes to our existing forks (so you'd check out a new branch for each one). Then, create a new submodule for scratch-blocks pointing to this new repo, and help pnpm to do what's necessary to link them all together.