Extending chat message blocks

Development
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3

Mostly I would like API that would allow a plugin to:

  1. Register a chat message block type name, owned by that plugin
  2. Optionally, provide a JSON schema validator for that block
  3. Register a renderer for that block

All of this can be patched in, but if there is an official API, the stability and safety would be better. My use case is forge activity notifications, but I imagine other applications would exist (RSS as an alternative to the RSS plugin, social media feeds, etc).