docs: update required CI4 version

Author: kenjis

README.md

@@ -35,7 +35,7 @@ access for a mobile application that you build.
 
 Usage of Shield requires the following:
 
-- A [CodeIgniter 4](https://github.com/codeigniter4/CodeIgniter4/)-based project
+- A [CodeIgniter 4.2.3+](https://github.com/codeigniter4/CodeIgniter4/) based project
 - [Composer](https://getcomposer.org/) for package management
 - PHP 7.4.3+
 

docs/install.md

@@ -12,6 +12,9 @@
 
 These instructions assume that you have already [installed the CodeIgniter 4 app starter](https://codeigniter.com/user_guide/installation/installing_composer.html) as the basis for your new project, set up your `.env` file, and created a database that you can access via the Spark CLI script.
 
+> **Note**
+> CodeIgniter Shield requires Codeigniter v4.2.3 or later.
+
 > **Note**
 > You must set ``Config\Security::$csrfProtection`` to `'session'` (or set `security.csrfProtection = session` in your `.env` file) for security reasons, if you use Session Authenticator.