name inconsistency

[atlhawksfanatic]

Github project is nba-db but for pretty much everything within the project is an nba_db reference. Leads to unintentional breaks in reference like the footer on the read the docs:

https://github.com/wyattowalsh/nba-db/blob/6af8db949ebae8e1ee0e8245677ef24d079d1c1e/docs/_templates/footer-item-github.html#L4

The https://www.github.com/wyattowalsh/nba_db doesn't exist. Seems like the consistent solution would be to change repository to nba_db to align with that as the consistently referenced name, but not sure if that breaks too much of references outside of Github and it's easier to just correct for the footer. Awesome resource here though!