doc: Update README

Author: jcdcdev

.github/README.md

@@ -18,6 +18,11 @@ The following editors are currently supported:
 - Textstring
 - Textarea
 
+> [!IMPORTANT]
+> Version 13 will only receive security updates and no new features.
+
+> Please review the [security policy](https://github.com/jcdcdev/jcdcdev.Umbraco.ReadingTime?tab=security-ov-file#supported-versions) for more information.
+
 ## Quick Start
 
 1. Install the [NuGet package](https://www.nuget.org/packages/jcdcdev.Umbraco.ReadingTime) in your Umbraco CMS website project.