add sunset message
MODIFY
README.md
README.md
+##### Atom and all repositories under Atom will be archived on December 15, 2022. Learn more in our [official announcement](https://github.blog/2022-06-08-sunsetting-atom/)
# Find and Replace package
[![CI](https://github.com/atom/find-and-replace/actions/workflows/ci.yml/badge.svg)](https://github.com/atom/find-and-replace/actions/workflows/ci.yml)

add sunset message