toolhead: Export the print_stalls value via get_status()

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

docs/Command_Templates.md

@@ -202,6 +202,9 @@ The following are common printer attributes:
   limits that are in effect. This may differ from the config file
   settings if a `SET_VELOCITY_LIMIT` (or `M204`) command alters them
   at run-time.
+- `printer.toolhead.stalls`: The total number of times (since the last
+  restart) that the printer had to be paused because the toolhead
+  moved faster than moves could be read from the G-Code input.
 - `printer.heaters.available_heaters`: Returns a list of all currently
   available heaters by their full config section names,
   e.g. `["extruder", "heater_bed", "heater_generic my_custom_heater"]`.

klippy/toolhead.py

@@ -502,6 +502,7 @@ class ToolHead:
         estimated_print_time = self.mcu.estimated_print_time(eventtime)
         res = dict(self.kin.get_status(eventtime))
         res.update({ 'print_time': print_time,
+                     'stalls': self.print_stall,
                      'estimated_print_time': estimated_print_time,
                      'extruder': self.extruder.get_name(),
                      'position': self.Coord(*self.commanded_pos),