Mark repository as archived in README

Added an archived notice to the README file.

Author: root-11

README.md

@@ -1,6 +1,7 @@
 # Tablite
 
-![Build status](https://github.com/root-11/tablite/actions/workflows/python-test.yml/badge.svg)
+# THIS REPO IS ARCHIVED.
+
 [![codecov](https://codecov.io/gh/root-11/tablite/branch/master/graph/badge.svg?token=A0QEWGO9R6)](https://codecov.io/gh/root-11/tablite)
 [![Downloads](https://pepy.tech/badge/tablite)](https://pepy.tech/project/tablite)
 [![Downloads](https://pepy.tech/badge/tablite/month)](https://pepy.tech/project/tablite)