add link to mindplay/middleman

as of [release 1.1](https://github.com/mindplay-dk/middleman/releases/tag/1.1.0) this library provides a middleware resolver that allows for integration with any container-interop implementation

Author: mindplay-dk

README.md

@@ -96,6 +96,7 @@ View open [request for comments](https://github.com/container-interop/container-
 - [zend-expressive](https://github.com/zendframework/zend-expressive)
 - [blast-facades](https://github.com/phpthinktank/blast-facades): Minimize complexity and represent dependencies as facades.
 - [mindplay/walkway](https://github.com/mindplay-dk/walkway): a modular request router.
+- [mindplay/middleman](https://github.com/mindplay-dk/middleman): minimalist PSR-7 middleware dispatcher.
 
 
 ## Workflow