docs: warn of PHP 7.4 EOL (#21)

Signed-off-by: Tom Carrio <[email protected]>

Author: tcarrio

README.md

@@ -23,6 +23,8 @@ This repository is marked as **experimental** since the repository structure its
 
 This library targets PHP version 7.4 and newer. As long as you have any compatible version of PHP on your system you should be able to utilize the OpenFeature SDK.
 
+⚠️ **PHP 7.4 is EOL and support will be discontinued in these libraries soon.**
+
 This package also has a `.tool-versions` file for use with PHP version managers like `asdf`.
 
 ### Installation and Dependencies