cal: improve util-linux page and split POSIX, osx and *BSD (#12172)

Co-authored-by: Juri Dispan <juri.dispan@posteo.net>
Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>

pages/freebsd/cal.md

@@ -0,0 +1,32 @@
+# cal
+
+> Display a calendar with the current day highlighted.
+> More information: <https://man.freebsd.org/cgi/man.cgi?cal>.
+
+- Display a calendar for the current month:
+
+`cal`
+
+- Display a calendar for a specific year:
+
+`cal {{year}}`
+
+- Display a calendar for a specific month and year:
+
+`cal {{month}} {{year}}`
+
+- Display the whole calendar for the current year:
+
+`cal -y`
+
+- Don't [h]ighlight today and display [3] months spanning the date:
+
+`cal -h -3 {{month}} {{year}}`
+
+- Display the 2 months [B]efore and 3 [A]fter a specific [m]onth of the current year:
+
+`cal -A 3 -B 2 {{month}}`
+
+- Display [j]ulian days (starting from one, numbered from January 1):
+
+`cal -j`