Initial library endpoints

[nichwall]

This PR includes:

• Some initial library endpoints
• Updates to the Author endpoints
• Fixes to existing schemas for exploded spec
• Adds series endpoints
• Adds workflow to lint the spec

Next steps are likely (in this general order):

1. Notification routes
2. Email routes
3. Podcast routes and schemas (used in lots of responses with the library)
4. Item routes and schemas
5. Collections routes and schemas
6. Playlists routes and schemas
7. RSS feeds
8. The rest of the Library routes

Preview of redocly generated docs:

[nichwall]

Also, feel free to squash this PR, there were a number of commits where I went "oh, this is the syntax for [insert thing] in OpenAPI 3.0" and then said "Wait, nevermind, I mixed up 2.0/3.0/3.1 again" a few commits later

[advplyr]

Somehow I never knew about the squash merge feature in github.. I thought this was something that had to be done with a force commit.

[advplyr]

Thanks!