timeout.1: Document non-POSIX options

MFC after:		3 days
Reviewed by:		Aaron Li <[email protected]>, ziaee
Differential Revision:	https://reviews.freebsd.org/D56090

bin/timeout/timeout.1

@@ -25,7 +25,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd April 3, 2025
+.Dd April 11, 2026
 .Dt TIMEOUT 1
 .Os
 .Sh NAME
@@ -269,6 +269,10 @@ The
 utility is expected to conform to the
 .St -p1003.1-2024
 specification.
+.Pp
+The
+.Fl v
+option and long option names are extensions to that specification.
 .Sh HISTORY
 The
 .Nm