Merge pull request #343 from sl0wik/patch-2

Update README with PHP specific configuration

Author: maigovannon

README.md

@@ -36,6 +36,7 @@ Google Cloud's buildpacks can be configured in a few ways:
     * [Go](https://cloud.google.com/docs/buildpacks/go)
     * [Java](https://cloud.google.com/docs/buildpacks/java)
     * [Ruby](https://cloud.google.com/docs/buildpacks/ruby)
+    * [PHP](https://cloud.google.com/docs/buildpacks/php)
 
 ## App Engine and Cloud Function Builders and Buildpacks