[readme] add es-shims implementation

Author: ljharb

README.md

@@ -1420,7 +1420,7 @@ class AsyncPluginHost {
   constructor(arg) {
     if (arg !== privateConstructorSentinel) throw new TypeError("Use AsyncPluginHost.create() instead");
   }
-  
+
   // NOTE: there's no such thing as an async constructor
   static async create() {
     const host = new AsyncPluginHost(privateConstructorSentinel);
@@ -1874,7 +1874,9 @@ The following is a high-level list of tasks to progress through each stage of th
 
 ## Implementations
 
-- Built-ins from this proposal are available in [`core-js`](https://github.com/zloirock/core-js#explicit-resource-management)
+- Built-ins from this proposal are available in:
+ - [`core-js`](https://github.com/zloirock/core-js#explicit-resource-management)
+ - es-shims [`disposablestack`](https://npmjs.com/disposablestack)
 
 <!-- # References -->