add ping command

src/commands/collection.ts

@@ -1,9 +1,12 @@
 import { Collection } from "@discordjs/collection";
+import { PingCommand } from "./impl/ping.ts";
 import { SongCommand } from "./impl/song.ts";
 import type { ICommand } from "./interface.ts";
 
 export const commands = new Collection<string, ICommand>();
 
 const songCommand = new SongCommand();
+const pingCommand = new PingCommand();
 
 commands.set(songCommand.name, songCommand);
+commands.set(pingCommand.name, pingCommand);