Enable playing downloaded audio files from outside of the app (add a local folder)

[mitchdowney]

[mitchdowney]

@drenina also requested this feature: https://github.com/podverse/podverse-rn/issues/1792#issue-1689401741

Please add the ability to add a local folder to the podcasts. I have other mp3 files that I also want to listen to through Podverse, most podcatchers let you choose a local storage and scan this folder for new files.

[adevries17]

@mitchdowney First want to say, thank you for all the hard work on making this application. I love it and have switched full time to using it on Android and the web. Second, I'd love this feature as well, whenever you have the time to implement it!

[mitchdowney]

@adevries17 glad you like the app! It's difficult to say when I can work on this one specifically as it will be quite a big change for our current setup. Hopefully I can focus on it sometime early 2024.