Add missing docstrings

src/shellfu/saturnin.sh

 }
 
 saturnin__usage() {
+    #
+    # Show usage message and exit
+    #
     #shellcheck disable=SC2046
     mkusage "$@"                                            \
             "[options] COMMAND [ARG...]"                    \
 
 _saturnin__conf_usage() {
     #
-    #
+    # Show usage message and exit
     #
     PRETTY_USAGE="self=${0##*/} conf" \
     mkusage "[options] [-e] SECTION.KEY [FNAME]"                               \