compress svg by SVGO

[JLHwung]

In this PR we compressed current svg assets using SVGO.

The netlify will terminate the post-process asset optimization on Oct. 17. The html/js/css are already minified by docusaurus and other tools. So we only have to optimize the SVG assets.

There are quite a few *.png assets as well. I think we can compress them losslessly into WebP, supported by all major browsers, or do that a few years later.

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[nicolo-ribaudo]

I think we can compress them losslessly into WebP, supported by all major browsers, or do that a few years later.

Can we have both the WebP and PNG versions, using https://developer.mozilla.org/en-US/docs/Web/API/HTMLImageElement/srcset?

[JLHwung]

https://developer.mozilla.org/en-US/docs/Web/API/HTMLImageElement/srcset

The MDN also mentions <picture> element for offering alternative image types: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/picture. It seems to me the srcset is meant to support different devices with different screen ratios / dpis, etc.