Added link to additional extension

Author: peldax

src/content/code/language-support/php/server/graphpinator.md

@@ -17,6 +17,7 @@ GraPHPinator is feature complete PHP implementation of GraphQL server. Its job i
     - [Constraint directives](https://github.com/infinityloop-dev/graphpinator-constraint-directives) - Typesystem directives to declare additional validation on top of GraphQL typesystem.
     - [Where directives](https://github.com/infinityloop-dev/graphpinator-where-directives) - Executable directives to filter values in lists.
     - File upload using [multipart-formdata](https://github.com/jaydenseric/graphql-multipart-request-spec) specs (currently bundled).
+    - [Query cost limit module](https://github.com/infinityloop-dev/graphpinator-query-cost) - Modules to limit maximum query cost by resticting maximum depth or number of nodes.
 - Project is composed from multiple smaller packages, which may be used standalone:
     - [Tokenizer](https://github.com/infinityloop-dev/graphpinator-tokenizer) - Lexical analyzer of GraphQL document.
     - [Parser](https://github.com/infinityloop-dev/graphpinator-parser) - Syntactic analyzer of GraphQL document.