solve Arduino IDE library warnings

1. get rid of unrecognized category warning in Arduino IDE. It doesn't seem to support multiple categories
2. add esp8266 to the list of architctures to avoid warnings about incompatible architecture. This library works on esp8266

library.properties

@@ -4,7 +4,7 @@ author=sui77
 maintainer=sui77,fingolfin <[email protected]>
 sentence=Operate 433/315Mhz devices.
 paragraph=Use your Arduino or Raspberry Pi to operate remote radio controlled devices. This will most likely work with all popular low cost power outlet sockets. 
-category=Device Control, Signal Input/Output
+category=Device Control
 url=https://github.com/sui77/rc-switch
-architectures=avr
-includes=RCSwitch.h
+architectures=avr,esp8266
+includes=RCSwitch.h