Improve HLS.js documentation

[krseager]

Is your feature request related to a problem? Please describe.

Documentation is currently incomplete and not documenting the following HLSConfig items:

1. timelineOffset
2. ignorePlaylistParsingErrors
3. errorController
4. preserveManualLevelOnError
5. assetPlayerId
6. primarySessionId
7. useMediaCapabilities

Describe the solution you'd like

We should add documentation for these items to docs/API.md.

Additional context

No response