Add ! operator to PinValue (#1246)

* Add ! operator to PinValue

* Use shorter form of implementation
Co-authored-by: NKrzysztof Wicher <mordotymoja@gmail.com>
Co-authored-by: NKrzysztof Wicher <mordotymoja@gmail.com>

src/System.Device.Gpio/System/Device/Gpio/PinValue.cs

@@ -81,6 +81,13 @@ namespace System.Device.Gpio
         /// </summary>
         public static bool operator !=(PinValue a, PinValue b) => !a.Equals(b);
 
+        /// <summary>
+        /// Returns the inverse of the value
+        /// </summary>
+        /// <param name="v">Input value</param>
+        /// <returns>High, when the input is low, low when the input is high</returns>
+        public static PinValue operator !(PinValue v) => (v._value == 0) ? High : Low;
+
         /// <inheritdoc />
         public override int GetHashCode() => _value.GetHashCode();