chore: Extract error handler and graphql instance to seperate files

packages/backend/src/helpers/graphql-instance.ts

@@ -0,0 +1,11 @@
+import { graphqlHTTP } from 'express-graphql';
+import rootResolver from '../graphql/root-resolver'
+import graphQLSchema from '../graphql/graphql-schema'
+
+const graphQLInstance = graphqlHTTP({
+  schema: graphQLSchema,
+  rootValue: rootResolver,
+  graphiql: true,
+})
+
+export default graphQLInstance;