Add pipeAsyncFunctions

snippets/pipeAsyncFunctions.md

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+### pipeAsyncFunctions
+
+Performs left-to-right function composition.
+
+Use `Array.reduce()` with the spread operator (`...`) to perform left-to-right function composition using `Promise.then()`. The functions can return a combination of: simple values, `Promise`'s, or they can be defined as `async` ones returning through `await`.
+All functions must be unary.
+
+```js
+const pipeAsyncFunctions = (...fns) => arg => fns.reduce((p, f) => p.then(f), Promise.resolve(arg));
+```
+
+```js
+const sum = pipeAsyncFunctions(
+  x => x + 1,
+  x => new Promise(resolve => setTimeout(() => resolve(x + 2), 1000)),
+  x => x + 3,
+  async x => (await x) + 4
+);
+(async () => {
+  console.log(await sum(5)); // 15 (after one second)
+})();
+```