Test migration to jest by hand

Apparently using regular expressions is way easier.

test/stableSort/stableSort.js

@@ -0,0 +1,6 @@
+const stableSort = (arr, compare) =>
+arr
+.map((item, index) => ({ item, index }))
+.sort((a, b) => compare(a.item, b.item) || a.index - b.index)
+.map(({ item }) => item);
+module.exports = stableSort;