Add coverage status badge to README.md

Author: Electronic-Mango

README.md

@@ -5,6 +5,7 @@
 [![Flake8](https://github.com/Electronic-Mango/simple-justwatch-python-api/actions/workflows/flake8.yml/badge.svg)](https://github.com/Electronic-Mango/simple-justwatch-python-api/actions/workflows/flake8.yml)
 [![isort](https://github.com/Electronic-Mango/simple-justwatch-python-api/actions/workflows/isort.yml/badge.svg)](https://github.com/Electronic-Mango/simple-justwatch-python-api/actions/workflows/isort.yml)
 [![Pytest](https://github.com/Electronic-Mango/simple-justwatch-python-api/actions/workflows/pytest.yml/badge.svg)](https://github.com/Electronic-Mango/simple-justwatch-python-api/actions/workflows/pytest.yml)
+[![Coverage Status](https://coveralls.io/repos/github/Electronic-Mango/simple-justwatch-python-api/badge.svg?branch=main)](https://coveralls.io/github/Electronic-Mango/simple-justwatch-python-api?branch=main)
 [![PyPI - Version](https://img.shields.io/pypi/v/simple-justwatch-python-api)](https://pypi.org/project/simple-justwatch-python-api/)
 
 A simple unofficial JustWatch Python API which uses [`GraphQL`](https://graphql.org/) to access JustWatch data.