Add fm set username command

Beginning of the command. Can't do anything other than setting and
updating your lastfm username.

commands/misc/fm.js

@@ -0,0 +1,21 @@
+const fmlogin = require("../../util/lastfm/fmlogin");
+
+module.exports = {
+    name: 'fm',
+    description: 'Last fm commands. See `<prefix>help fm` for more info.',
+    moreHelp: ["Set username: `<prefix>fm set <lastfm_username>`",],
+    async execute({ message, args }) {
+        let sendText = "Something went wrong.";
+        switch (args[0]) {
+            case "help":
+                sendText = this.moreHelp;
+                break;
+            case "set":
+                sendText = await fmlogin(message.author.id, args[1]);
+                break;
+            default:
+                break;
+        }
+        message.channel.send(sendText);
+    }
+};