feat: Convert root query and mutation resolvers to js

packages/backend/src/graphql/resolvers.js

@@ -0,0 +1,9 @@
+import mutationResolvers from './mutation-resolvers';
+import queryResolvers from './query-resolvers';
+
+const resolvers = {
+  Query: queryResolvers,
+  Mutation: mutationResolvers,
+};
+
+export default resolvers;