Add LBRY protocol

[ben221199]

Summary

This pull request adds a multiaddr for the LBRY network protocol, as described at https://lbry.tech/spec.

Before Merge

• Allow at least 24 hours for community input
• If this is a new protocol, has the change been applied to https://github.com/multiformats/multicodec as well? If so, please link the multicodec PR. Add LBRY protocol multicodec#332

[Stebalien]

multiaddrs are for addressing machines and processes (i.e., endpoints you talk to) not for naming content. You probably just want a multicodec in the "namespace" category.

E.g., /ip4/1.2.3.4/udp/1234/quic means: speak the QUIC protocol over udp port 1234 to a machine at the IP 1.2.3.4.

[ben221199]

I added a reaction on multiformats/multicodec#332.