- Implement dagger.#FS support
- Migrate `context.imports` to dagger.#FS
- Backward compat: dagger.#FS can be passed in lieu of a
dagger.#Artifact
- For instance, an import (`dagger.#FS`) can be passed to the current
`yarn.#Package` implementation
Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>
