update readme

Author: fey

README.md

@@ -19,6 +19,17 @@ make install
 make test
 ```
 
+## Run tests with coverage
+
+See [sonar-project.properties](./sonar-project.properties#1:2):
+
+```bash
+make test-coverage
+# see ./coverage dir
+```
+
+---
+
 [![Hexlet Ltd. logo](https://raw.githubusercontent.com/Hexlet/assets/master/images/hexlet_logo128.png)](https://hexlet.io/?utm_source=github&utm_medium=link&utm_campaign=nodejs-package)
 
 This repository is created and maintained by the team and the community of Hexlet, an educational project. [Read more about Hexlet](https://hexlet.io/?utm_source=github&utm_medium=link&utm_campaign=nodejs-package).