Adding documentation to the repo

[eduardojsbarroso]

We need to add documentation:

• To the code modules
• Readme describing the repo
• Documentation to installation
• Documentation on how to contribute
• Generate documentation with sphinx
• Add documentation generation to github actions

[eduardojsbarroso]

@caioolivv Hi, I created this PR for the documentation. I think we should organize everything like the CLMM documentation, docs.

I did some initial implementation but I was not vera detailed here.

• We should have equations describing the functions if fit
• We have to check if all masses are indeed just solar or someplace they are divided by h (For instance completeness and purity in the aguena paper are defined with M/h, so I do not know if this is a problem Aguena16)

Let me know if you are able to work on this. Thanks