v4.1.0

Bug fixes:

• Fixed #762 by always considering the last valid signature rather than just the last signature
• Fixed #765 by disregarding non-self revocation signatures and by returning an error when parsing a key with an authorized revocation key subpacket (not supported by the library)
• Fixed #752 by adding some documentation to avoid confusion about text vs. binary formats

API changes:

• Key.prototype.getRevocationCertificate is now async
• SubKey.prototype.getExpirationTime is now async and takes primaryKey, [date] as parameters instead of just [date]
• When parsing a key with an authorized revocation key subpacket, we now return an error in the (await openpgp.key.read/readArmored(key)).err array, but also still return the key in the .keys array. This is because we ignore valid third-party revocation signatures made by authorized keys, so the key might not be safe to use in some cases.