docs: Update for latest changs to skew_correction

Signed-off-by:  Eric Callahan <arksine.code@gmail.com>

docs/G-Codes.md

@@ -477,12 +477,26 @@ of retraction required.
 
 The following commands are available when the "skew_correction" config
 section is enabled.
+  - `SET_SKEW [XY=<ac_length,bd_length,ad_length>] [XZ=<ac,bd,ad>]
+    [YZ=<ac,bd,ad>] [CLEAR=<0|1>]`:  Configures the [skew_correction] module
+    with measurements (in mm) taken from a calibration print.  One may
+    enter measurements for any combination of planes, planes not entered will
+    retain their current value.  If `CLEAR=1` is entered then all skew
+    correction will be disabled.
   - `GET_CURRENT_SKEW`: Reports the current printer skew for each plane in
     both radians and degrees.  The skew is calculated based on parameters
-    provided to the [skew_correction] section of printer.cfg.
+    provided via the `SET_SKEW` gcode.
   - `CALC_MEASURED_SKEW [AC=<ac_length>] [BD=<bd_length>] [AD=<ad_length>]`:
     Calculates and reports the skew (in radians and degrees) based on a
     measured print.  This can be useful for determining the printer's current
     skew after correction has been applied.  It may also be useful before
     correction is applied to determine if skew correction is necessary.   See
-    skew_correction.md for details on skew calibration objects and measurements.
+    skew_correction.md for details on skew calibration objects and
+    measurements.
+  - `SKEW_PROFILE [LOAD=<name>] [SAVE=<name>] [REMOVE=<name>]`: Profile
+    management for skew_correction.  LOAD will restore skew state from the
+    profile matching the supplied name. SAVE will save the current skew state
+    to a profile matching the supplied name.  Remove will delete the profile
+    matching the supplied name from persistent memory.  Note that after SAVE
+    or REMOVE operations have been run the SAVE_CONFIG gcode must be run
+    to make the changes to peristent memory permanent.