It isn't needed on landing yet, but it gets included automatically so I figured that there's no downside.

For keyserver it will be accessed via getCommConfig. On web and landing it will be access via process.env.COMM_NEYNAR_KEY.

It will be configured either by setting keyserver/secrets/neynar.json, or by the env var COMM_JSONCONFIG_secrets_neynar.

This approach follows what we're done for the Alchemy and WalletConnect API keys.

This addresses ENG-7424.

I tested this in combination with later diffs on both keyserver and web:

1. I specified keyservers/secrets/neynar.json
2. For keyserver, I tested that Farcaster usernames worked in notifs
3. For web, I tested that Farcaster usernames were resolved in robotext