[IDEA] locally imported extensions gallery (for offline editor)

[idoinfactexist]

when loading an extension file from your computer it would be nice to have a gallery of extensions you've imported in the past

1. so projects that use extensions that are not on the gallery can automatically load them, instead of throwing out an error
2. so you can import extensions that haven't been added to the gallery yet to use in the offline editor (ex: window controls)