SpringBoot Contribute missing resource hints for GraphQL schema files and GraphiQL HTML page

Spring for GraphQL is implementing AOT support in its upcoming 1.1.0 version, with spring-projects/spring-graphql#495.

We need to add the missing resource hints for the GraphQL support configured in Spring Boot:

• GraphQL schema files, see spring.graphql.schema.locations
• the GraphiQL UI page, see spring.graphql.graphiql.enabled