feat: initial boilerplate

spec/relay/libraries/hooks.ts

@@ -0,0 +1,10 @@
+export type Hooks = {
+  /**
+   * Executes when any error is thrown before or during the lifetime
+   * of the route. This allows for custom handling of errors if the
+   * route has unique requirements to error handling.
+   *
+   * @param error - Error which has been thrown.
+   */
+  onError?: (error: unknown) => Response;
+};