Package variant without protobuf support

[forana]

For my use case, I do not need the protobuf support. It seems like it's entirely additional and this package can be used without them completely - it would be nice to have a version available that does not pull in this extra dependency.

(Ideally, there would be a package igdb-api-v4 with an "extra" available for protobuf support - igdb-api-v4[protobuf] - but I understand this might break existing setups)