Extra explanation on "port already in use" error

Closes #27

lib/project_view/control_row.dart

@@ -129,6 +129,16 @@ class RunningProcess {
         _consoleOutputController.add(event);
       }
 
+      if (event.contains("This usually happens when the configured port ") &&
+          event.contains(" is already in use by some other program.")) {
+        _consoleOutputController.add(
+            " There is probably already a BlueMap process running.\n"
+            " Check that you don't have any BlueMap mods installed on your Minecraft client,\n"
+            "  and check in your Task Manager for any orphaned BlueMapCLI processes and close them.\n"
+            " If you are sure there is no other BlueMap process running and this error persists,\n"
+            "  try restarting your computer.");
+      }
+
       if (event.contains("WebServer bound to")) {
         _stateController.add(RunningProcessState.running);
         final String? portText = portExtractionRegex.firstMatch(event)?.group(1);