Host signing pubkeys directly with docs, to simplify checking them out

[andrey-utkin]

Please just make it possible to download the full public keys from wherever openzfs.github.io/openzfs-docs/ is hosted.

https://openzfs.github.io/openzfs-docs/Project%20and%20Community/Signing%20Keys.html takes me to a search by short key id page on pgp.mit.edu which is super slow. From years of my experience, keyservers often happen to be DDoSed and/or underresourced, and adversaries add their keys with matching shortened key ids. When that webpage loaded after a few minites, I can inspect which keys are found, but I apparently can't immediately download full public key found.

The docs page advises to run a command gpg --keyserver pgp.mit.edu --recv ..., but with regard to the above I don't trust gpg enough to believe it will do the right thing without prior inspection.

But anyway, running this command fails with a cryptic message, probably due to timeout:

 # gpg --keyserver pgp.mit.edu --recv D4598027
gpg: keybox '/root/.gnupg/pubring.kbx' created
gpg: keyserver receive failed: No data