Merge pull request reduxjs#2579 from adrienjt/patch-1

Add redux-data-structures to Ecosystem

Author: markerikson

docs/introduction/Ecosystem.md

@@ -112,6 +112,7 @@ On this page we will only feature a few of them that the Redux maintainers have
 * [redux-mock-store](https://github.com/arnaudbenard/redux-mock-store) — Mock redux store for testing your app
 * [redux-actions-assertions](https://github.com/dmitry-zaets/redux-actions-assertions) — Assertions for Redux actions testing
 * [redux-bootstrap](https://github.com/remojansen/redux-bootstrap) — Bootstrapping function for Redux applications
+* [redux-data-structures](https://redux-data-structures.js.org/) — Reducer factory (higher-order functions) for counters, maps, lists (queues, stacks), sets, etc.
 
 ### DevTools