Add a warning when someone tries to add an existing top placeholder

src/main/java/us/ajg0702/leaderboards/commands/main/subcommands/Add.java

@@ -8,6 +8,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 import java.util.regex.Matcher;
 
 import static us.ajg0702.leaderboards.LeaderboardPlugin.message;
@@ -39,7 +40,11 @@ public void execute(CommandSender sender, String[] args, String label) {
                 return;
             }
             if(!plugin.validatePlaceholder(placeholder, sender)) {
+                String lowerPlaceholder = placeholder.toLowerCase(Locale.ROOT);
                 sender.sendMessage(message("&cThe placeholder '"+placeholder+"' does not give a numerical value. Make sure that the placeholder returns a number that is not formatted."));
+                if(lowerPlaceholder.contains("top") || lowerPlaceholder.contains("lb")) {
+                    sender.sendMessage(message("&eThat placeholder looks like it might be an existing top placeholder! Please read step 1 of the setup guide!"));
+                }
                 return;
             }
             boolean r = plugin.getCache().createBoard(placeholder);