Banlist feature

[danimesq]

Exclude specific repo owner/reponame from criteria.

For example, https://github.com/wgao19/mimikyu isn't a valid repo; it haves no functions beyond just reserving a name.

So, "wgao19/mimikyu" could be excluded by adding it to a banlist/denylist.

@cheeaun

[styfle]

https://github.com/cheeaun/repokemon/issues/6#issuecomment-234540632