README/Composer: suggest the Requests PSR18 adapter package

README.md

@@ -141,6 +141,24 @@ set of tests. We're not quite there yet, but [we're getting close][codecov].
 [codecov]: https://codecov.io/github/WordPress/Requests/
 
 
+Requests and PSR-7/PSR-18
+-------------------------
+
+[PSR-7][psr-7] describes common interfaces for representing HTTP messages.
+[PSR-18][psr-18] describes a common interface for sending HTTP requests and receiving HTTP responses.
+
+Both PSR-7 as well as PSR-18 were created after Requests' conception.
+At this time, there is no intention to add a native PSR-7/PSR-18 implementation to the Requests library.
+
+However, the amazing [Artur Weigandt][art4] has created a [package][requests-psr-18], which allows you to use Requests as a PSR-7 compatible PSR-18 HTTP Client.
+If you are interested in a PSR-7/PSR-18 compatible version of Requests, we highly recommend you check out [this package][requests-psr-18].
+
+[psr-7]:           https://www.php-fig.org/psr/psr-7/
+[psr-18]:          https://www.php-fig.org/psr/psr-18/
+[art4]:            https://github.com/Art4
+[requests-psr-18]: https://packagist.org/packages/art4/requests-psr18-adapter
+
+
 Contribute
 ----------
 

composer.json

@@ -54,7 +54,8 @@
   "suggest": {
     "ext-curl": "For improved performance",
     "ext-openssl": "For secure transport support",
-    "ext-zlib": "For improved performance when decompressing encoded streams"
+    "ext-zlib": "For improved performance when decompressing encoded streams",
+    "art4/requests-psr18-adapter": "For using Requests as a PSR-18 HTTP Client"
   },
   "autoload": {
     "psr-4": {