[FEATURE] Install the API only

[nclement-cytoo]

Maybe I am missing this somewhere in the documentation, I'd like to include Cellpose models in my project as a dependency, to do this it would be nice to have the API installable without adding all the GUI or CLI components.

Is it something I could do easily ? Or should I clone and prune the repo of everything I don't need ? My goal is to have cellpose as a git submodule so I can keep the features up to date.