Make all plotting dependencies optional

[ocefpaf]

We should make all plotting dependencies, like pandas_flavor, matplotlib, and cartopy (any other?), optional as a plotting extras.

@FloraSauerbronn this would require you to edit the requirements.txt file, to remove any plotting dependencies that may be listed there, and add a new entry in the pyproject.toml like:

[project.optional-dependencies]
plotting = [list_the_dependencies_here ]

Can you tackle that?

[neerja-1984]

@ocefpaf went through the above issue .. is it sorted out ?

I wish to contribute to the repo and was anticipating any ideas / enhancements iooc is looking in the project

[ocefpaf]

Glad you are interested. Can you check the dependency descriptions and figure out if these is done or not? It would be a way to show your proficiency with pyproject.toml and Python dependency management.

[neerja-1984]

@ocefpaf this is my first time working with .toml files
have made this pr as per my understanding #134

do let me know if it meets the requirement