openconnect: add page (#4780)

pages/common/openconnect.md

@@ -0,0 +1,24 @@
+# openconnect
+
+> A VPN client, for Cisco AnyConnect VPNs and others.
+> More information: <https://www.infradead.org/openconnect/manual.html>.
+
+- Connect to a server:
+
+`openconnect {{vpn.example.org}}`
+
+- Connect to a server, forking into the background:
+
+`openconnect --background {{vpn.example.org}}`
+
+- Terminate the connection that is running in the background:
+
+`killall -SIGINT openconnect`
+
+- Connect to a server, reading options from a config file:
+
+`openconnect --config={{path/to/file}} {{vpn.example.org}}`
+
+- Connect to a server and authenticate with a specific SSL client certificate:
+
+`openconnect --certificate={{path/to/file}} {{vpn.example.org}}`