Stop using @import in scss

[Samuel-Therrien-Beslogic]

• The project passes automated tests (build, linting, etc.).
• You updated the project's documentation with new changes.
• You've linked any issue this PR closes
• You reviewed your own PR and made sure there's no test/debug code or any obvious mistakes.

Make sure that the code wasn't copied from elsewhere (check one):

• This is your own original code
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Closes #281

This is a very important fix performance-wise:

• Downloads a lot less
• Debugging CSS is a lot easier now that styles aren't set 7 times each
• Vite's "Fast refresh" stops being unresponsive for a while
• Probably fixes my Edge dev tool crashes (at least haven't had one in a while and it feels more responsive)

[andy2great]

LGTM