QR Code Component using plain HTML and CSS

This was a nice refresher on my plain HTML and CSS skills. Working on the project it was clear that my Flexbox skills have gotten rusty in the short time I've been learning.

I think my code fits the design fairly well, but I am unsure if I have configured the margins appropriately.

I would like to look into how I can incorporate libraries and frameworks into the project to streamline the process. I wonder if Bootstrap or SASS would be applicable to clean up my code a bit.