QR component made using HTML and CSS

Looks good as is. Great job!

For future consideration, you might refactor the style.css file to utilize css variables. This would benefit in the future, if the design system changes or you add more classes with similar attributes, allowing you to edit a single variable versus everywhere the same value is being used.

For example, working with the design system colors:

:root {
    --color-white: hsl(0, 0%, 100%);
    --color-slate-300: hsl(212, 45%, 89%);
    --color-slate-500: hsl(216, 15%, 48%);
    --color-slate-900: hsl(218, 44%, 22%);
}

So then whenever you use the dark grey color you can do:

p {
    color: var(--color-slate-900);
}

.text-content {
    color: var(--color-slate-900);
}