Add coverity badge to README

Coverity finally started working correctly. Thanks @wlemkows.

Author: pbalcer

README.md

@@ -3,6 +3,7 @@
 [![Build and test](https://github.com/oneapi-src/unified-runtime/actions/workflows/cmake.yml/badge.svg)](https://github.com/oneapi-src/unified-runtime/actions/workflows/cmake.yml)
 [![CodeQL](https://github.com/oneapi-src/unified-runtime/actions/workflows/codeql.yml/badge.svg)](https://github.com/oneapi-src/unified-runtime/actions/workflows/codeql.yml)
 [![Bandit](https://github.com/oneapi-src/unified-runtime/actions/workflows/bandit.yml/badge.svg)](https://github.com/oneapi-src/unified-runtime/actions/workflows/bandit.yml)
+[![Coverity](https://scan.coverity.com/projects/28213/badge.svg)](https://scan.coverity.com/projects/oneapi-src-unified-runtime)
 
 <!-- TODO: add general description and purpose of the project -->