GitHub Actions test.yml workflow should also check CSS

[nbkhope]

We're using this to check the HTML for errors: https://github.com/marketplace/actions/html5-validator

It also can check CSS if you specify css: true.

Change the test.yml and add that. https://github.com/nbktechworld/full-stack-web-dev/blob/master/.github/workflows/test.yml

Just add css: true below the line for the root property. Follow the same indentation (spaces in the beginning of line) level.