docs: add codecov badge

Author: d-perl

README.md

@@ -1,6 +1,5 @@
 # bec_log_ingestor
 
-[![Linting](https://github.com/d-perl/bec_log_ingestor/actions/workflows/check-and-lint.yaml/badge.svg)](https://github.com/d-perl/bec_log_ingestor/actions/workflows/check-and-lint.yaml) [![Test coverage](https://img.shields.io/endpoint?url=https://gist.githubusercontent.com/d-perl/cd22d345696706dc24434c103b64ccea/raw/
-)](https://github.com/d-perl/bec_log_ingestor/actions/workflows/test-and-coverage.yaml)
+[![Linting](https://github.com/d-perl/bec_log_ingestor/actions/workflows/check-and-lint.yaml/badge.svg)](https://github.com/d-perl/bec_log_ingestor/actions/workflows/check-and-lint.yaml) [![codecov](https://codecov.io/gh/d-perl/bec_log_ingestor/graph/badge.svg?token=PN9871U8A3)](https://codecov.io/gh/d-perl/bec_log_ingestor)
 
 Tiny service to pull BEC logs from Redis and push them to Elastic