Update README to indicate repository is archived

Added a warning about the repository being archived and provided a link to the new version.

Author: igor-pavlenko

README.md

@@ -1,3 +1,10 @@
+> [!WARNING]
+> **This repository is archived and no longer maintained.**
+> 
+> A new, actively maintained version is available at: [forcebit/http-message-signatures-rfc9421-go](https://github.com/forcebit/http-message-signatures-rfc9421-go)
+
+
+
 # Sign/Verify signature with http-signatures golang lib
 
 [![Linter & Tests](https://github.com/igor-pavlenko/httpsignatures-go/workflows/linter%20&%20tests/badge.svg?branch=master)](https://github.com/igor-pavlenko/httpsignatures-go/actions)