cmd/tsconnect: allow hostname to be specified

The auto-generated hostname is nice as a default, but there are cases
where the client has a more specific name that it can generate.

Signed-off-by: Mihai Parparita <mihai@tailscale.com>

cmd/tsconnect/src/types/wasm_js.d.ts

@@ -47,6 +47,7 @@ declare global {
     stateStorage?: IPNStateStorage
     authKey?: string
     controlURL?: string
+    hostname?: string
   }
 
   type IPNCallbacks = {