add $sender variable to random response module

src/modules/random.rs

@@ -63,6 +63,7 @@ impl EventLoop for RandomModule {
                             if let Some(captures) = pattern.captures(&message.content) {
                                 let mut response = String::new();
                                 captures.expand(&rand::sample(&mut rng, &responses, 1)[0], &mut response);
+                                response = response.replace("$sender", &message.author.name);
                                 message.reply(&response);
                             }
                         },