Added comment

Author: AndreasArvidsson

packages/common/src/util/itertools.ts

@@ -66,6 +66,13 @@ export function isEmptyIterable(iterable: Iterable<unknown>): boolean {
   return true;
 }
 
+/**
+ * Returns the first element of the given iterable, or `undefined` if the
+ * iterable is empty
+ * @param iterable The iterable to get the first element of
+ * @returns The first element of the iterable, or `undefined` if the iterable
+ * is empty
+ */
 export function next<T>(generator: Iterable<T>): T | undefined {
   for (const value of generator) {
     return value;