checkkey.sh: Add EDDSA algo (RFC8032)

[pouria]

Summary

This fixes the UNKNOWN type returned by checkkey.sh
The EDDSA (22) has a dedicated standard (RFC8032),
and is also allowed for use in RFC9580 which obsoletes RFC4880.

Test Plan

To test you can use a key with algorithm number 22:

% ./documentation/tools/checkkey.sh C7E57F23C24F542D
key C7E57F23C24F542D: EDDSA

[pouria]

Why don't we allow new committers to use curve algorithms?
I can see that there are multiple ed25519 keys currently in use by committers, as reported by ./doc/documentation/tools/pgpkeyreport.
However, committer's guide states that checkkey.sh must be used to ensure the key is valid.
The checkkey.sh script does not allow committers to use curve algorithms. Is this ok or should we write an exception for curve algorithms?

[des]

There is no reason not to allow EDDSA. It just did not yet exist when this script was written.

[pouria]

documentation/tools/checkkey.sh

194

@des I can add an exception here for ECC/ECDSA/EDDSA algorithms to avoid returning badkey error to users if you want.

[siva]

documentation/tools/checkkey.sh

194

Found this review by making the same local change myself. Yes, you will need to add a line here for EDDSA) ;;

[pouria]

Avoid returning badkey error for EDDSA.