Make help command use descriptions and usages

src/main/java/wtf/beatrice/hidekobot/commands/message/MagicBallCommand.java

@@ -30,6 +30,18 @@ public class MagicBallCommand implements MessageCommand
         return false;
     }
 
+    @NotNull
+    @Override
+    public String getDescription() {
+        return "Ask a question to the Magic Ball.";
+    }
+
+    @Nullable
+    @Override
+    public String getUsage() {
+        return "<question>";
+    }
+
     @NotNull
     @Override
     public CommandCategory getCategory() {