Added a join command #7

- Added a JSON example for Known Client IDs
- Implemented a custom slash command builder to add the available presets as options in the discord command

Server/clientIds.json.EXAMPLE

@@ -0,0 +1,6 @@
+{
+    "[ID from Discord]": {
+        "name": "[Nickname of the Bot]",
+        "id": "[Client ID from Discord Dev Portal]"
+    }
+}