add more embed stuff (#939)

* add fun embed stuff

* add more docstrings

* fix gawdl3y

* Update RichEmbed.js

src/structures/User.js

@@ -232,6 +232,7 @@ class User {
   // These are here only for documentation purposes - they are implemented by TextBasedChannel
   sendMessage() { return; }
   sendTTSMessage() { return; }
+  sendEmbed() { return; }
   sendFile() { return; }
   sendCode() { return; }
 }