api/builtins/Control: add feed_forward gain

This can be useful for motors with high internal static friction.

pybricks/builtins.py

@@ -53,7 +53,7 @@ class Control():
         """
         pass
 
-    def pid(self, kp, ki, kd, integral_range, integral_rate):
+    def pid(self, kp, ki, kd, integral_range, integral_rate, feed_forward):
         """Get or set the PID values for position and speed control.
 
         If no arguments are given, this will return the current values.
@@ -69,6 +69,10 @@ class Control():
                 are accumulated.
             integral_rate (:ref:`speed` or :ref:`linspeed`): Maximum rate at
                 which the error integral is allowed to grow.
+            feed_forward (:ref:`percentage`):
+                This adds a feed forward signal to the PID feedback signal, in
+                the direction of the speed reference. This value is expressed
+                as a percentage of the absolute maximum duty cycle.
         """
         pass