Remove LGTM badges and add Coverage badge (#414)

* Remove LGTM badges and add Coverage badge

Remove LGTM badges and add Coverage badge

* Update README.md

Author: emlowe

README.md

@@ -5,10 +5,9 @@
 ![PyPI - Format](https://img.shields.io/pypi/format/blspy?logo=pypi)
 ![GitHub](https://img.shields.io/github/license/Chia-Network/bls-signatures?logo=Github)
 
-[![Total alerts](https://img.shields.io/lgtm/alerts/g/Chia-Network/bls-signatures.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/Chia-Network/bls-signatures/alerts/)
-[![Language grade: JavaScript](https://img.shields.io/lgtm/grade/javascript/g/Chia-Network/bls-signatures.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/Chia-Network/bls-signatures/context:javascript)
-[![Language grade: Python](https://img.shields.io/lgtm/grade/python/g/Chia-Network/bls-signatures.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/Chia-Network/bls-signatures/context:python)
-[![Language grade: C/C++](https://img.shields.io/lgtm/grade/cpp/g/Chia-Network/bls-signatures.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/Chia-Network/bls-signatures/context:cpp)
+[![CodeQL](https://github.com/Chia-Network/bls-signatures/actions/workflows/codeql.yml/badge.svg)](https://github.com/Chia-Network/bls-signatures/actions/workflows/codeql.yml)
+
+[![Coverage Status](https://coveralls.io/repos/github/Chia-Network/bls-signatures/badge.svg?branch=main)](https://coveralls.io/github/Chia-Network/bls-signatures?branch=main)
 
 NOTE: THIS LIBRARY IS NOT YET FORMALLY REVIEWED FOR SECURITY