wdctl: add page (#7112)

pages/linux/wdctl.md

@@ -0,0 +1,16 @@
+# wdctl
+
+> Show the hardware watchdog status.
+> More information: <https://manned.org/wdctl>.
+
+- Display the watchdog status:
+
+`wdctl`
+
+- Display the watchdog status in a single line in key-value pairs:
+
+`wdctl --oneline`
+
+- Display only specific watchdog flags (list is driver specific):
+
+`wdctl --flags {{flag_list}}`