feature: Build standalone files using `azul build`

[Ransomwave]

Azul currently has no way of generating standalone files from source, since it's only capable of building inside Studio itself.

Considering we have 1:1 reproductible builds using --from-sourcemap, the next logical step is to implement standalone file creation.

Use-cases:

• Creating GitHub actions that create RBXM files (like rbxasset, but using Azul)
• Allowing the Azul Plugin to be built with itself. (No more downloading from place file)

Info:

• RBXLX/RBXMX schema: https://github.com/RobloxAPI/spec/blob/master/formats/rbxlx.md