add support for accessing feeds and content over IPFS

### What problem does this address?

Enabling people to access podcasts published through the decentralized web will allow more resilient and free access to podcast content, and provide more options for podcast hosting. Podcasts could even be hosted and accessed from any computer that can run a local IPFS daemon, or using new platforms like web3.storage.

### What is your proposed solution?

1) Implement access to IPFS via gateways, as Opera on Android has done:
https://blog.ipfs.tech/2020-03-30-ipfs-in-opera-for-android/

2) in the future, add the option for accessing IPFS via a full local IPFS node running on the device for true decentralized access

### Did you search for existing feature suggestions?

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

The issue names no files, tests, or entry points. Start by reviewing the linked Opera gateway approach and the app's existing feed and content networking paths; define gateway access as the initial scope and treat local-node support as future work.

Written by the indexing model from the issue text.