Better README.md

[etsuo]

Hmm.. forgot to mention npm i @sakuraapi/auth-oAuth-authority... oops. Also needs more documentation about how it works, how it integrates, and how it interacts with auth-native-authority

• mention npm i @sakuraapi/auth-oAuth-authority
• more documentation about how it works
• how it integrates
• how it interacts with auth-native-authority