chore: add persistent-keepalive for wireguard

adapter/outbound/wireguard.go

@@ -53,6 +53,7 @@ type WireGuardOption struct {
 	Workers             int    `proxy:"workers,omitempty"`
 	MTU                 int    `proxy:"mtu,omitempty"`
 	UDP                 bool   `proxy:"udp,omitempty"`
+	PersistentKeepalive int    `proxy:"persistent-keepalive,omitempty"`
 }
 
 type wgDialer struct {
@@ -159,6 +160,9 @@ func NewWireGuard(option WireGuardOption) (*WireGuard, error) {
 	if has6 {
 		ipcConf += "\nallowed_ip=::/0"
 	}
+	if option.PersistentKeepalive != 0 {
+		ipcConf += fmt.Sprintf("\npersistent_keepalive_interval=%d", option.PersistentKeepalive)
+	}
 	mtu := option.MTU
 	if mtu == 0 {
 		mtu = 1408