Using operators without having `transformers` installed

[Ronsor]

I'm currently trying to use just the operators defined in fla.ops; however, because of the __init__.py script for the main package, it's not possible to do this without importing things from the HF transformers package, which makes the import slower (and broke it entirely until I upgraded the package).

It would be nice if there were a way to just import the operators without the layer modules or anything else.