Common: modalai updates for 4.5.0

explain VISO_QUAL_MIN and add link to extnav-optflow transitions lua script

common/source/docs/common-modalai-voxl.rst

@@ -56,6 +56,7 @@ Connect to the autopilot with a ground station (i.e. Mission Planner) and check
 - Optionally set :ref:`SERIAL2_OPTIONS <SERIAL2_OPTIONS>` = 1024 (Don't forward mavlink to/from) to disable the camera's odometry messages from being sent to the GCS
 - :ref:`VISO_TYPE <VISO_TYPE>` = 3 (VOXL)
 - Set :ref:`VISO_POS_X <VISO_POS_X>`, :ref:`VISO_POS_Y <VISO_POS_Y>`, :ref:`VISO_POS_Z <VISO_POS_Z>` to the camera's position on the drone relative to the center-of-gravity.  See :ref:`sensor position offset compensation <common-sensor-offset-compensation>` for more details
+- Optionally increase :ref:`VISO_QUAL_MIN <VISO_QUAL_MIN>` to 10 (or higher) to only consume estimates from the camera when the quality is 10% (or higher)
 
 If only the VOXL camera will be used for position estimation and heading (e.g. No GPS):
 
@@ -86,6 +87,8 @@ After the parameters are modified, reboot the autopilot.
 
 More details on :ref:`GPS/Non-GPS Transitions can be found here <common-non-gps-to-gps>`
 
+To use an optical flow and rangefinder for backup in case the VOXL fails, a Lua applet for `ExternalNav/Optical flow transitions is here <https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_Scripting/applets/ahrs-source-extnav-optflow.lua>`__
+
 Videos
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