add informations and a production env example

platformio.ini

@@ -20,6 +20,11 @@ extra_configs =
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;Uncomment the env line corresponding to your board and modules required,              ;
 ;you can also adapt the modules by removing the corresponding lines in the env detail  ;
+; if you go to the build flag section of your env you will see that some user_config.h ;
+; parameters can be overwritten here, for example the gateway name.                    ;
+; If you want to avoid the lost of your environments at each update you can put them   ;
+; into a separate file called prod_env.ini, it will be automatically read by pio       ;
+; an example (prod_env.ini.example) is available into the same folder as this file.    ;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 ;default_envs = sonoff-basic-rfr3