Implement/Fix Podcasts

I might be able to tackle this soon, but the current API does not handle Podcasts.

Things that need to be fixed:

1. The album querySelector fails when podcasts are playing because the element doesn't exist, causing the songInfo API to not return results.
2. There is also two new buttons, rewind-10 and forward-30 that are not implemented.
3. We should implement an API method such as isPodcast which can be tracked by checking the current .now-playing-actions for the class podcast.
4. There are no ratings for podcasts, so those setters/getters "break" as well.

I'm not sure of the feasibility of adding tests as Podcasts are regionally available and we can't upload a podcast (afaik) to test metadata and the new buttons. We may have to settle for finding a podcast and navigating to it directly in order to test.