mh_copyright: add page (#7910)

Co-authored-by: Emily Grace Seville <emilyseville7cf@gmail.com>

pages/common/mh_copyright.md

@@ -0,0 +1,12 @@
+# mh_copyright
+
+> Adjust copyright headers for MATLAB or Octave code.
+> More information: <https://misshit.org>.
+
+- Update the year (range) to include the current year for the specified files:
+
+`mh_copyright --primary-entity="{{entity}}" --update-year {{path/to/file_or_directory1.m path/to/file_or_director2.m ...}}`
+
+- Update the year (range) to include the current year for all files:
+
+`mh_copyright --primary-entity="{{entity}}" --update-year`