Document hidden dependency

README.md

@@ -82,7 +82,7 @@ Creates a stream from a PSR-7 stream / request / response.
 before you can use this stream, you'll need to install the `guzzlehttp/psr-7` package which contains a stream wrapper implementation.
 
 ```bash
-composer require guzzlehttp/psr-7
+composer require psr/http-message guzzlehttp/psr-7
 ```
 
 ```php

src/Factory/Psr7Stream.php

@@ -25,7 +25,7 @@ public static function createFromStream(StreamInterface $stream): ResourceStream
         // @codeCoverageIgnoreStart
         // StreamWrapper is always available in test-suite.
         if (!class_exists(StreamWrapper::class)) {
-            throw new \RuntimeException('Please run: "composer require guzzle/psr-7" if you want to load a PSR-7 resource stream.');
+            throw new \RuntimeException('Please run: "composer require psr/http-message guzzle/psr-7" if you want to load a PSR-7 resource stream.');
         }
         // @codeCoverageIgnoreEnd