Migrate from deprecated node-sass to sass

[Bartek532]

Description

Migrate from deprecated node-sass to sass

Closes #529 <-- link the issue number here

Browser checklist

This PR has been tested in the following browsers:

• [x] Chrome
• [x] Firefox
• [ ] Safari

Testing checklist

• [ ] End-to-end tests have been created if necessary

[micalevisk]

I guess you'll need to commit the changes on package-lock.json as well.