motion_report: Add get_status() method with current requested toolhead position

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

docs/Status_Reference.md

@@ -189,6 +189,18 @@ The following information is available in
 - `last_stats.<statistics_name>`: Statistics information on the
   micro-controller connection.
 
+## motion_report
+
+The following information is available in the `motion_report` object
+(this object is automatically available if any stepper config section
+is defined):
+- `live_position`: The requested toolhead position interpolated to the
+  current time.
+- `live_velocity`: The requested toolhead velocity (in mm/s) at the
+  current time.
+- `live_extruder_velocity`: The requested extruder velocity (in mm/s)
+  at the current time.
+
 ## output_pin
 
 The following information is available in