Add ipv6 support for shadowsocksr server

Update shadowsocksr

luci-app-ssr-plus/root/etc/init.d/shadowsocksr

@@ -220,6 +220,7 @@ gen_service_file() {
 	cat <<-EOF >$2
 		{
 		"server": "0.0.0.0",
+		"server_ipv6": "::",
 		"server_port": $(uci_get_by_name $1 server_port),
 		"password": "$(uci_get_by_name $1 password)",
 		"timeout": $(uci_get_by_name $1 timeout 60),