weave and weaveWith (#465)

Added weave and weaveWith from tidal

packages/core/util.mjs

@@ -206,3 +206,9 @@ export function parseFractional(numOrString) {
 }
 
 export const fractionalArgs = (fn) => mapArgs(fn, parseFractional);
+
+export const splitAt = function (index, value) {
+  return [value.slice(0, index), value.slice(index)];
+};
+
+export const zipWith = (f, xs, ys) => xs.map((n, i) => f(n, ys[i]));