Fixed issue with path to styles.scss when running tests

[nevadascout]

The angular.json file has an incorrect path to the styles.scss file in the test step.
I've updated it to add the src/ as is required.

This was the error I got when trying to run the tests with npm test:

ERROR in multi ./styles.css
Module not found: Error: Can't resolve '/Users/ns/dev/ngx-example/styles.css' in '/Users/ns/dev/ngx-example'
 @ multi ./styles.css styles[0]

[nevadascout]

@ocombe Do you have a few minutes to review & merge this pull request? 😃