tail.1: Add an example for +n 1

MFC after:	3 days
Sponsored by:	Klara, Inc.

usr.bin/tail/tail.1

@@ -155,7 +155,7 @@ arguments may also be specified with size suffixes supported by
 .Sh EXIT STATUS
 .Ex -std
 .Sh EXAMPLES
-To display the last 500 lines of the file
+Display the last 500 lines of the file
 .Ar foo :
 .Pp
 .Dl $ tail -n 500 foo
@@ -165,6 +165,12 @@ Keep
 open, displaying to the standard output anything appended to the file:
 .Pp
 .Dl $ tail -F /var/log/messages
+.Pp
+Read
+.Pa /var/log/messages
+from the beginning and then follow the file as usual:
+.Pp
+.Dl $ tail -F -n +1 /var/log/messages
 .Sh SEE ALSO
 .Xr cat 1 ,
 .Xr head 1 ,