add capitalizeFirstLetter utility

src/lib/util.ts

@@ -87,3 +87,9 @@ export function targetMust<T extends HTMLElement>(event: Event): T {
 	}
 	return target;
 }
+
+/** capitalizeFirstLetter capitalizes the first letter of a string */
+export const capitalizeFirstLetter = (str: string): string => {
+	const lower = str.toLowerCase();
+	return lower.charAt(0).toUpperCase() + lower.slice(1);
+};