filament_motion_sensor: Add filament_motion_sensor (#3857)

Add functionality to support a Filament Motion Sensor for detecting extruder jams as well as runouts.  Works by an encoder toggling the switch_pin 0/1 as the filament is pulled through the sensor.

Signed-off-by: Joshua Wherrett <thejoshw.code@gmail.com>

docs/Config_Reference.md

@@ -3461,6 +3461,34 @@ information.
 #   provided.
 ```
 
+## [filament_motion_sensor]
+
+Filament Motion Sensor. Support for filament insert and runout
+detection using an encoder that toggles the output pin during filament
+movement through the sensor.
+
+See the [command reference](G-Codes.md#filament-sensor) for more
+information.
+
+```
+[filament_motion_sensor my_sensor]
+detection_length: 7.0
+#   The minimum length of filament pulled through the sensor to trigger
+#   a state change on the switch_pin
+#   Default is 7 mm.
+extruder:
+#   The name of the extruder section this sensor is associated with.
+#   This parameter must be provided.
+switch_pin:
+#pause_on_runout:
+#runout_gcode:
+#insert_gcode:
+#event_delay:
+#pause_delay:
+#   See the "filament_switch_sensor" section for a description of the
+#   above parameters.
+```
+
 ## [tsl1401cl_filament_width_sensor]
 
 TSLl401CL Based Filament Width Sensor. See the