feat: Added Radix Theme to the app, added specific scss file and made some styling adjustments

[MelanieTheLion]

In this PR:

• Added @radix-ui/theme package to our app. This is a very big package, with a LOT of dependencies. The plan is to eventually go to our own component library based on Radix primitives, but due to time constraints, we now use this theme.
• Added new fonts
• Did some styling adjustments to get Radix to work alongside Bootstrap (our current styling thing)
• Added Radix colors and setup in its own scss file. I now have one old CSS file (App.css) and one new Main.scss file.

What it looks like:

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud