Add hooks and warnings.ts

Author: Tomdango

src/deprecated/warnings.ts

@@ -0,0 +1,5 @@
+export const PromoDeprecationWarning =
+  'The Promo component is deprecated, and will be removed in the next major version of nhsuk-react-components. The Card component is the intended replacement.';
+
+export const PanelDeprecationWarning =
+  'The Promo component is deprecated, and will be removed in the next major version of nhsuk-react-components. The Card component is the intended replacement.';

src/util/hooks/UseDevWarning.tsx

@@ -0,0 +1,13 @@
+import { useEffect } from 'react';
+import isDev from '../IsDev';
+
+const useDevWarning = (warning: string) => {
+  useEffect(() => {
+    if (isDev()) {
+      // eslint-disable-next-line no-console
+      console.warn(warning);
+    }
+  }, []);
+};
+
+export default useDevWarning;