feat: Turbowarp folder support

[aitchFactor]

Could be nice to be able to compile directory structures into sprite/costume names that Turbowarp displays as folders.

This would be useful for any sprites that import all directories in a folder, ie, "assets/*/*.png".

Subdirectories could also be represented with the same // separator even though Turbowarp won't display these as folders.

[aspizu]

why do u think this is useful?

[aitchFactor]

1. Easier for non-goboscript users to sift through projects created with goboscript
2. Streamlines naming costumes by directory which generally makes it easier to query and manage many costumes.