UIKit - logo: replace ratio property by width and height properties

[mfranzke]

I've recognized that there's a new option related to the logo to provide the ratio as a string, compare to https://github.com/pattern-lab/patternlab-node/blob/dev/packages/uikit-workshop/src/scripts/lit-components/pl-logo/pl-logo.js - but it seems that the ratio isn't being used/set in that component.

I'd like to suggest to change the "ratio" property to both "width" and "height" properties with their equivalent HTML attributes being used, as the browser determines the aspectratio itself nowadays (as suggested by Jen Simmons, see e.g. https://css-tricks.com/what-if-we-got-aspect-ratio-sized-images-by-doing-almost-nothing/).

I'll open a PR for this.