Refactor task list example application

packages/utilities/index.d.ts

@@ -0,0 +1,3 @@
+export type RequireOnly<T, Keys extends keyof T = keyof T> = Partial<T> & Required<Pick<T, Keys>>;
+export declare const isError: (error: unknown) => error is Error;
+export declare const getErrorMessage: (error: unknown, defaultMessage: string) => string;