screws_tilt_adjust: add max_deviation to report status

Signed-off-by: Stefan Dej <meteyou@gmail.com>

docs/Status_Reference.md

@@ -386,6 +386,8 @@ object:
 - `error`: Returns True if the most recent `SCREWS_TILT_CALCULATE`
   command included the `MAX_DEVIATION` parameter and any of the probed
   screw points exceeded the specified `MAX_DEVIATION`.
+- `max_deviation`: Return the last `MAX_DEVIATION` value of the most
+  recent `SCREWS_TILT_CALCULATE` command.
 - `results["<screw>"]`: A dictionary containing the following keys:
   - `z`: The measured Z height of the screw location.
   - `sign`: A string specifying the direction to turn to screw for the

klippy/extras/screws_tilt_adjust.py

@@ -61,6 +61,7 @@ class ScrewsTiltAdjust:
 
     def get_status(self, eventtime):
         return {'error': self.max_diff_error,
+            'max_deviation': self.max_diff,
             'results': self.results}
 
     def probe_finalize(self, offsets, positions):