polar: add velocity scaling (#7172)

Print near the origin lead in to fast motor movements, therefore the
movement needs to be scaled down. The start of the scaling is done via
a rotation velocity limit from the config.

Signed-off-by: Nils Hensch <nils.hensch@gmx.de>

docs/Config_Reference.md

@@ -569,6 +569,11 @@ max_z_accel:
 #   This sets the maximum acceleration (in mm/s^2) of movement along
 #   the z axis. It limits the acceleration of the z stepper motor. The
 #   default is to use max_accel for max_z_accel.
+# max_angular_velocity: 0
+#   This limits the maximum angular velocity (in rad/s) of a move.
+#   Lower values will result in longer print times, but prevents too
+#   fast motions near the center. A value of 0 deactivates the
+#   scaling. The default is to not apply maximum angular velocity limits.
 
 # The stepper_bed section is used to describe the stepper controlling
 # the bed.