clock: add page (#17673)

Co-authored-by: Kristopher <kristopherleads@gmail.com>

pages/cisco-ios/clock.md

@@ -0,0 +1,20 @@
+# clock
+
+> Set the system clock.
+> More information: <https://www.cisco.com/c/en/us/td/docs/ios/fundamentals/command/reference/cf_book/cf_c1.html#clock>.
+
+- Enter privileged execution mode:
+
+`clock set {{23}}:{{59}}:{{59}} {{31}} {{april}} {{2000}}`
+
+- Auto negotiate with the far end of the link, defaulting to active-clock:
+
+`clock active prefer`
+
+- Auto negotiate with the far end of the link, defaulting to passive-clock:
+
+`clock passive prefer`
+
+- Show the current clock mode negotiated by the firmware:
+
+`clock show interfaces`