Callysto menu extension

[AyushChaudhari2001]

Added 2 new extensions:

Banners - Automatically creates Callysto banners in new Jupyter notebooks
Menu - Provides options to create predefined cells with code snippets for commonly used libraries

[ianabc]

Hi Ayush, thanks for the PR! So far I've tried to avoid adding the jupyter_contrib_extensions module (and jupyter_nbextensions_configurator), would it be practical to rewrite these to stand alone? Or are they closely tied to those projects?

[AyushChaudhari2001]

Hi @ianabc, yeah the extensions I've made are pretty closely tied to those modules so I'm not sure how practical it would be to rewrite the code. Out of curiosity, is there a reason for trying to avoid using those modules?

[ianabc]

I forget, but I think it was getting difficult to untie some of the support requests for the extensions from other parts of the infrastructure.

[AyushChaudhari2001]

@ianabc Is there any way I can test it out on the Callysto infrastructure? If not maybe I'll look at the code you wrote and try to rewrite mine to not be reliant on the modules