warp-cli: improve page description, add "See also" and add example (#12303)

pages/common/warp-cli.md

@@ -1,6 +1,8 @@
 # warp-cli
 
-> Official command-line client for Cloudflare's WARP service.
+> Connect, disconnect and switch modes of a connection to Cloudflare's WARP service.
+> WARP is a VPN that encrypts traffic for privacy, security, and speed.
+> See also: `fastd`, `ivpn`, `mozzilavpn`, `mullvad`.
 > More information: <https://developers.cloudflare.com/warp-client/>.
 
 - Register the current device to WARP (must be run before first connection):
@@ -19,6 +21,10 @@
 
 `warp-cli status`
 
+- Switch to a specific mode:
+
+`warp-cli set-mode {{mode}}`
+
 - Display help:
 
 `warp-cli help`