Add Webassembly-based runtime for GDScript.

[ValorZard]

Discussion for #3370

current fork that has this kinda working as of writing this: https://github.com/contextfreeinfo/godot/tree/gdscript-wasm

video explaining their thought process and methodology : https://youtu.be/hmyxqrzgL28

[tjpalmer]

Hi! I'm Tom, the person who made the experiment so far and the video.

Maybe some of the bigger items among many left to do:

• Variants
• Memory management
• Coordination among multiple vs how many wasm modules
• Exposing Godot API generally, and how would that relate to GDExtensions in wasm?
• Lambdas
• Async
• JIT
• AOT compilation, especially for iOS
• Running in browser
• Full debugger information
• Can this eventually replace the current GDScript VM entirely?

Maybe not everything above needs done before it's useful.

Meanwhile, I added my work directly into the GDScript module. For compiling to Wasm, that might be especially convenient. I'm less certain it makes sense for the running side, but I'm new enough to the Godot code base, and I'm uncertain enough about some of the future planning that I don't know what's ideal with that.

Beyond that, to me the next steps, if next steps are worth doing (would the Godot team accept any of this work?), are to keep working through GDScript unit test cases and passing them one at a time.

I'd also love to figure out how to build faster, but scons is still being awkward to me.

I also don't know how much churn the gdscript code usually sees. Like, as I work through this over time (of which I have little), would merging back get very hard over time?

Anyway, that's all my brain dump for the moment.

[tjpalmer]

Also to clarify, I don't need to be the one who makes this happen or who gets credit for it. I just think this would make the world a better place (in the infrastructure sense only). If it were up to me, I'd drop most other work on GDScript other than bug fixes in order to get some variation of this done. Then I'd get back to other tasks with this new infrastructure in place. But that's just me.

On the other hand, if this is just me working on it, it might never get done. Again, life is busy and all. And I'm easily distracted.