Add php version requirements

Author: Flynsarmy

readme.md

@@ -16,8 +16,14 @@ This package allows CSV based seeds.
 
 Require this package in your composer.json and run composer update (or run `composer require flynsarmy/csv-seeder:2.*` directly):
 
+**For PHP 7.4+**
+
     "flynsarmy/csv-seeder": "2.0.*"
 
+**For older PHP versions**
+
+    "flynsarmy/csv-seeder": "1.*"
+
 
 ### Usage