Add Caliban to Scala Libraries (chentsulin#556)

Author: matteobaglini

README.md

@@ -302,6 +302,7 @@ If you want to contribute to this list (please do), send me a pull request.
 * [sangria](https://github.com/sangria-graphql/sangria) - Scala GraphQL server implementation.
 * [sangria-relay](https://github.com/sangria-graphql/sangria-relay) - Sangria Relay Support.
 * [graphql-scala](https://github.com/hrosenhorn/graphql-scala) - An attempt to get GraphQL going with Scala.
+* [https://github.com/ghostdogpr/caliban](https://github.com/hrosenhorn/graphql-scala) - Caliban is a purely functional library for creating GraphQL backends in Scala.
 
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