Document version 2 long term support

Author: johnstevenson

README.md

@@ -14,6 +14,8 @@ now extracted and made available as a stand-alone library.
 
 Removed support for legacy PHP versions and added type declarations.
 
+Long term support for version 2 (PHP 5.3.2 - 7.2.4) follows [Composer 2.2 LTS](https://blog.packagist.com/composer-2-2/]) policy.
+
 ## Installation
 
 Install the latest version with: