add selected index along with enumerated options list on json format

Author: neu-rah

library.properties

@@ -1,9 +1,9 @@
 name=ArduinoMenu library
-version=4.17.15
+version=4.17.16
 author=Rui Azevedo, [email protected]
 maintainer=neu-rah, [email protected]
 sentence=Generic menu/interactivity system
-paragraph=Easy to define menu system with sub-menus and associated function to call. Works either over serial or multiple combinations of IO
+paragraph=Easy to define menu system with sub-menus and associated function to call. Works from serial to Web depending on the hardware.
 category=Display
 url=https://github.com/neu-rah/ArduinoMenu
 dot_a_linkage=false

src/menuIO/jsonFmt.cpp

@@ -38,7 +38,7 @@
       // o<<node.sz();
       for(idx_t n=0;n<node.sz();n++)
         o<<(n?",":"")<<"\""<<node[n]<<"\"";
-      o<<"]";
+      o<<"],\"sel\":\""<<((menuVariantBase*)&node)->sync()<<"\"";
     }
   };
 #endif