Initialisation

Added the packages and files for the backend server

node_modules/graphql/validation/rules/SingleFieldSubscriptionsRule.d.ts

@@ -0,0 +1,13 @@
+import type { ASTVisitor } from '../../language/visitor';
+import type { ValidationContext } from '../ValidationContext';
+/**
+ * Subscriptions must only include a non-introspection field.
+ *
+ * A GraphQL subscription is valid only if it contains a single root field and
+ * that root field is not an introspection field.
+ *
+ * See https://spec.graphql.org/draft/#sec-Single-root-field
+ */
+export declare function SingleFieldSubscriptionsRule(
+  context: ValidationContext,
+): ASTVisitor;