pause_resume: update documentation

Add updates to example-extras.cfg and G-Codes.md documenting pause_resume.  Also add M600 (filament change) to sample-macros.cfg.

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

config/example-extras.cfg

@@ -1142,3 +1142,9 @@
 # default_prefix: echo:
 #    Directly sets the default prefix. If present, this value will override
 #    the "default_type".
+
+# Pause/Resume functionality with support of position capture and restore
+#[pause_resume]
+#recover_velocity: 50.
+#  When capture/restore is enabled, the speed at which to return to
+#  the captured position (in mm/s).  Default is 50.0 mm/s.

config/sample-macros.cfg

@@ -34,3 +34,24 @@
 #gcode:  SET_PIN PIN=BEEPER_pin VALUE={S}
 #        G4 P{P}
 #        SET_PIN PIN=BEEPER_pin VALUE=0
+
+# M600: Filament Change.  This macro will pause the printer, move
+# the tool to the change position, and retract the filament 50mm.
+# Adjust the retraction settings for your own extruder.  After filament
+# has been changed, the print can be resumed from its previous position
+# with the "RESUME" gcode
+#
+#[gcode_macro M600]
+#default_parameter_X: 50
+#default_parameter_Y: 0
+#default_parameter_Z: 10
+#gcode:
+# PAUSE
+# G91
+# G1 E-.8 F2700
+# G1 Z{Z}
+# G90
+# G1 X{X} Y{Y} F3000
+# G91
+# G1 E-50 F1000
+# G90