Update lmc-messages.mdx

adding information for sending LMC audio messages

Author: andrewfr

docs/protocols/lmc-messages.mdx

@@ -65,3 +65,4 @@ code|python|Python code that should be executed.|`assistant`|
 code|r|R code that should be executed.|`assistant`|
 code|applescript|AppleScript code that should be executed.|`assistant`|
 code|shell|Shell code that should be executed.|`assistant`|
+audio|wav|audio in wav format for websocket.|`user`|