Update complementary-tools.md (#639)

Author: leocavalcante

docs/complementary-tools.md

@@ -6,6 +6,7 @@
 * [Laravel GraphQL](https://github.com/rebing/graphql-laravel) - Laravel wrapper for Facebook's GraphQL
 * [OverblogGraphQLBundle](https://github.com/overblog/GraphQLBundle) – Bundle for Symfony
 * [WP-GraphQL](https://github.com/wp-graphql/wp-graphql) - GraphQL API for WordPress
+* [Siler](https://github.com/leocavalcante/siler) - Straightforward way to map GraphQL SDL to resolver callables, also built-in support for Swoole
 
 # GraphQL PHP Tools