chore(site): optimize logo

[XhmikosR]

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Summary

Should save ~50% from the uncompressed file, ~35% from the compressed one (gzip). I didn't change the IDs to smaller ones since the logo is inlined.

Let me know if you prefer the previous gradientTransform

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[XhmikosR]

BTW might be worth switching to Ubuntu 20.04, Node.js 16 for the docs. Should speed up deployments a bit.

EDIT: Oh, and it seems search is broken? I opened #3946 for this