Add fine-grained oauth scopes

[timjuenemann]

ATProto recently added some docs for permissions. It would be great to have this added, cause its pretty scary to basically give out full control over your account and all services on the PDS.

• https://atproto.com/specs/permission
• https://atproto.com/specs/lexicon#permission-set
• specs: permissions bluesky-social/atproto-website#465
• Permission set guide bluesky-social/atproto-website#484