Updates documentation

Author: sagikazarmark

README.md

@@ -30,6 +30,32 @@ Currently the following discovery strategies are available:
 - Message Factory discovery
 
 
+### Http Adapter discovery
+
+HTTP Adapters provided by us are registered in the discovery by default.
+
+``` php
+use Http\Discovery\HttpAdapterDiscovery;
+
+HttpAdapterDiscovery::register('my_adapter', 'My\Adapter\Class');
+
+$adapter = HttpAdapterDiscovery::find();
+```
+
+
+### Message Factory discovery
+
+Two common message factories are bundled with this package. ([Guzzle](https://github.com/guzzle/psr7), [Diactoros](https://github.com/zendframework/zend-diactoros))
+
+``` php
+use Http\Discovery\MessageFactoryDiscovery;
+
+MessageFactoryDiscovery::register('my_factory', 'Psr\Request\Implementation\Class', 'My\Factory\Class');
+
+$adapter = MessageFactoryDiscovery::find();
+```
+
+
 ## Testing
 
 ``` bash