Rename reference from master to main

[RavishaNayak]

Hey Guys , as a part of language inclusiveness , could you please accept the request to update all references changed from master to main .
for instance io.lindstrom.m3u8.model.MasterPlaylist to io.lindstrom.m3u8.model.MainPlaylist or io.lindstrom.m3u8.model.PrimaryPlaylist

I can raise a PR for the changes, but would like to hear your thoughts before this

[carlanton]

Hi!

Thank you for your PR (#45). I like this, but I also want this library to follow the terminology used in the specification it tries to implement: RFC 8216. When the RFC is updated, this library will follow.

I couldn't find any discussion on this topic regarding HLS, but it looks like Apple are now calling it Primary playlists in their developer documentation. Hopefully the RFC will follow soon! :)

I'll keep this issue open as a reminder.

Cheers,
Anton