Update federation.mdx

Author: kamilkisiela

website/src/pages/docs/integrations/federation.mdx

@@ -22,4 +22,4 @@ const config: CodegenConfig = {
 export default config
 ```
 
-It will add the required GraphQL directives to your codegen schema and generate a compatible resolvers signature for Apollo Federation.
+It will add the required GraphQL directives to your codegen schema and generate a compatible resolvers signature for [Apollo Federation](https://the-guild.dev/graphql/hive/federation).