Add Back4App to GraphQL Service Providers

Back4App is a Backend as a Service Platform that helps you Build and Scale modern applications based on GraphQL.

Author: alyssoncm

site/code/index.html.js

@@ -705,6 +705,7 @@ Executor.execute(schema, query) map println
   - [Elide](https://elide.io): A Java library that can expose a JPA annotated data model as a GraphQL service over any relational database. 
   - [Hasura](https://hasura.io) ([github](https://github.com/hasura)): Hasura connects to your databases & microservices and instantly gives you a production-ready GraphQL API.
   - [FaunaDB](https://docs.fauna.com/fauna/current/graphql): Create an instant GraphQL backend by importing a gql schema. The database will create relations and indexes for you, so you'll be ready to query in seconds, without writing any database code. Serverless pricing, free to get started.
+  - [Back4App](https://www.back4app.com/docs/parse-graphql/graphql-getting-started): Back4App is a Backend as a Service Platform that helps you Build and Scale modern applications based on GraphQL.
 
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