Make help command use descriptions and usages

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

@@ -34,6 +34,18 @@ public class InviteCommand implements MessageCommand
         return false;
     }
 
+    @NotNull
+    @Override
+    public String getDescription() {
+        return "Get the bot's invite link.";
+    }
+
+    @Nullable
+    @Override
+    public String getUsage() {
+        return null;
+    }
+
     @NotNull
     @Override
     public CommandCategory getCategory() {