New feature: Playlists

### What problem does this address?

Playlists will create the ability to add episodes from different podcasts to a single playlist. This way, it enables you to create curated playlists of episodes from different podcasts about a certain topic. Like the best interviews you listened to, or the best episodes you might wanna relisten to.

It's essentially the same as the Up Next List, only that you can create multiple lists, name them and share them, and episodes don't get removed when you listen to them.

### What is your proposed solution?

Create a separate tab under the 'Podcasts' screen in the bottom navigation bar. And call it 'Playlists', with the other tab being 'Podcasts'.

In the Playlists tab, you can create new playlists and add episodes to it from podcasts you are subscribed to or podcasts you searched for. And you can make them and share them through a creating a link.
Also, when viewing an episode, an option is added to 'Add to playlist', which is next to Up Next, Mark Played, and Archive.

### Did you search for existing feature suggestions?

- [X] I have searched for existing feature suggestions.

No files or tests are named. Start by locating the Podcasts screen bottom navigation and the existing Up Next, Mark Played, and Archive episode actions; the feature is complete when users can create and name multiple playlists, add episodes, retain listened episodes, and share playlist links.

Written by the indexing model from the issue text.