refactor(README): introduce CodeCov badge into README

README.md

@@ -2,11 +2,10 @@
 
 [![pipeline status](https://gitlab1.ptb.de/m4d/zema_emc_annotated/badges/main/pipeline.svg)](https://gitlab1.ptb.de/m4d/zema_emc_annotated/-/commits/main)
 [![Documentation Status](https://readthedocs.org/projects/zema-emc-annotated/badge/?version=latest)](https://zema-emc-annotated.readthedocs.io/en/latest/?badge=latest)
-[![coverage report](https://gitlab1.ptb.de/m4d/zema_emc_annotated/badges/main/coverage.svg)](https://gitlab1.ptb.de/m4d/zema_emc_annotated/-/commits/main)
+[![codecov](https://codecov.io/gh/PTB-M4D/zema_emc_annotated/branch/main/graph/badge.svg?token=HQZE3FXL7N)](https://app.codecov.io/gh/PTB-M4D/zema_emc_annotated?search=&displayType=list&trend=7%20days)
 [![Latest Release](https://gitlab1.ptb.de/m4d/zema_emc_annotated/-/badges/release.svg)](https://github.com/PTB-M4D/zema_emc_annotated/releases/latest)
 [![DOI](https://zenodo.org/badge/591514193.svg)](https://doi.org/10.5281/zenodo.7556142)
 
-
 This software provides a convenient API to access the annotated ZeMA dataset about 
 remaining useful life of an electro-mechanical cylinder on Zenodo
 ([![DOI