Update documentation link in README.md (#515)

Point to docs

Author: kamilkisiela

README.md

@@ -11,7 +11,7 @@ A fully open-source MIT-licensed GraphQL API router that can act as a [GraphQL f
 
 It can be run as a standalone binary or a Docker Image. Query planner can be used as a standalone Crate library.
 
-[Binary Releases](https://github.com/graphql-hive/router/releases) | [Docker Releases](https://github.com/graphql-hive/router/pkgs/container/router) | [Configuration reference](./docs/README.md)
+[Binary Releases](https://github.com/graphql-hive/router/releases) | [Docker Releases](https://github.com/graphql-hive/router/pkgs/container/router) | [Documentation]([./docs/README.md](https://the-guild.dev/graphql/hive/docs/router))
 
 ## Try it out