Initialisation

Added the packages and files for the backend server

node_modules/graphql/jsutils/invariant.mjs

@@ -0,0 +1,9 @@
+export function invariant(condition, message) {
+  const booleanCondition = Boolean(condition);
+
+  if (!booleanCondition) {
+    throw new Error(
+      message != null ? message : 'Unexpected invariant triggered.',
+    );
+  }
+}