added join and leave commands

commands/join.js

@@ -0,0 +1,8 @@
+module.exports = {
+    name: 'join',
+    description: 'joins a voice channel',
+    execute: async (message, voiceChannel, args) => {
+        connection = await voiceChannel.join();
+        connection.play('https://www.youtube.com/watch?v=Hl1s4BT9Fc4');
+    }
+};