more optimization/error handling

lib/helpers/format-number.ts

@@ -0,0 +1,5 @@
+import { siteLocale } from "../config";
+
+// adds thousands separator
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat/NumberFormat
+export const commafy = Intl.NumberFormat(siteLocale, { useGrouping: true }).format;