DRAFT: implement sequence

src/sequence/fold.ts

@@ -0,0 +1,7 @@
+export function fold<T, R>(value: Iterable<T>, initial: R, accumulate: (acc: R, it: T) => R): R {
+    let acc = initial;
+    for (const it of value) {
+        acc = accumulate(acc, it);
+    }
+    return acc;
+}