Add MMDVM status JSON messages.

MMDVMHost.h

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015-2021 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015-2021,2023 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -142,6 +142,8 @@ private:
 
   void createLockFile(const char* mode) const;
   void removeLockFile() const;
+
+  void writeJSON(const std::string& mode);
 };
 
 #endif