Add dependency to "FreeRTOS", bump version to 0.9.1

Author: Floessie

library.properties

@@ -1,5 +1,5 @@
 name=frt
-version=0.9.0
+version=0.9.1
 author=Flössie <[email protected]>
 maintainer=Flössie <[email protected]>
 sentence=Lightweight, easy-to-use wrapper around the Arduino_FreeRTOS_Library.
@@ -8,3 +8,4 @@ category=Timing
 url=https://github.com/Floessie/frt
 architectures=avr
 includes=frt.h
+depends=FreeRTOS