add slug for graphql http service

so that we can support query parameters for http service requests. 
This will ensure we can support GET requests, and any other query parameters that might be used by express-graphql

Author: acao

site/_redirects

@@ -1,3 +1,5 @@
 /swapi-graphql  https://swapi-graphql.netlify.com   200
 /swapi-graphql/* https://swapi-graphql.netlify.com/:splat   200
+
 /swapi-graphql/graphql https://swapi-graphql.netlify.com/.netlify/functions/index 200
+/swapi-graphql/graphql/* https://swapi-graphql.netlify.com/.netlify/functions/index/:splat 200