docs: update readme

Author: imann128

README.md

@@ -1,6 +1,6 @@
 # tsauditor
 [![CI](https://github.com/imann128/tsauditor/actions/workflows/ci.yml/badge.svg)](https://github.com/imann128/tsauditor/actions/workflows/ci.yml)
-[![codecov](https://codecov.io/gh/imann128/tsauditor/branch/main/graph/badge.svg)](https://codecov.io/gh/imann128/tsauditor)
+[![codecov](https://codecov.io/github/imann128/tsauditor/graph/badge.svg?token=3QKPEB8B4H)](https://codecov.io/github/imann128/tsauditor)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](LICENSE)
 
 A data-quality auditing library for **time-series tabular data**, with a focus on