docs(readme): add code-coverage option

Add code-coverage option in the READMEi.md.

Close #3018

Author: Mathou54

README.md

@@ -187,6 +187,10 @@ ng test
 
 Tests will execute after a build is executed via [Karma](http://karma-runner.github.io/0.13/index.html), and it will automatically watch your files for changes. You can run tests a single time via `--watch=false` or `--single-run`.
 
+You can run tests with coverage via `--code-coverage`. The coverage report will be in the `coverage/` directory.
+
+Linting during tests is also available via the `--lint` flag. See [Linting and formatting code](#linting-and-formatting-code) chapter for more informations.
+
 ### Running end-to-end tests
 
 ```bash