Optimize SVG images

[dilyanpalauzov]

with SVGO - https://github.com/svg/svgo

As result less data will be transferred to the browser.

[ghys]

Thanks for this initiative (and #1431), but since images were mostly sourced from different places which probably curated them well enough, applying a blanket optimization pass could have unexpected side effects or other implications. So those would have to be assessed, analyzed and processed which takes time.

[florian-h05]

Closing this PR as it went stale.