Support for NIP-99 Classified Listings

[bu5hm4nn]

They should be easy to rudimentarily display as they are similar to long-form events.

Here's an example note: nostr:nevent1qqs0acd9h2gd0w00vrkv5tdh8tk6dh3l9tntg83lvuqlsjlzfm3xszsppemhxue69uhkummn9ekx7mp0qy08wumn8ghj7mn0wd68yttsw43zuam9d3kx7unyv4ezumn9wshszyrhwden5te0dehhxarj9ekk7mf0mly5ch

[mikedilger]

Unless we are going to parse the structured metadata and give people the full classified listing I don't see the point. And we don't have NIP-89 support yet so gossip can't open these classified listings in some other app.