Use valid category in library.properties

The previous category value caused the warning:

WARNING: Category 'Control' in library ControlDigitalOutput is not valid. Setting to 'Uncategorized'

List of valid category values:
https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5:-Library-specification#libraryproperties-file-format

library.properties

@@ -4,7 +4,7 @@ author=thiminhnhut <thiminhnhut@gmail.com>
 maintainer=thiminhnhut <thiminhnhut@gmail.com>
 sentence=Control Digital Output Library for Arduino, ESP8266, ESP32.
 paragraph=Control Digital Output.
-category=Control
+category=Signal Input/Output
 url=https://github.com/thiminhnhut/control-digital-output
 architectures=*
 includes=ControlDigitalOutput.h