Improve Spinner performance

[lbebber]

Is your feature request related to a problem? Please describe.
Right now, due to how the Spinner component is implemented, it increases the CPU usage, due to causing re-layouts on the page

(notice the layouts/sec and style recalc/sec measurements at the bottom, along with CPU usage at the top)

This is because animating an element of an SVG triggers this event (at least on Chrome 88 on desktop) and is not (fully?) GPU accelerated.

Describe the solution you'd like
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Spinning a DOM element--for example, an entire SVG element, instead of just a part of it--fixes this issue.

This could be done without making any changes to the visuals of the spinner element as it is.

Describe alternatives you've considered
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Additional context
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[hasparus]

Thanks for the issue @lbebber! Great catch!

[hasparus]

🚀 Issue was released in v0.15.5 🚀