Utility for listing connected Yubikeys

 ykls is a utility for listing connected Yubikeys, along with some relevant
 information, such as enabled modes, firmware version, serial number,
 identities present in the various key slots, ...
 .
 For example:
 $ ykls
 Reader: Yubico YubiKey FIDO+CCID 00 00
 Version: 4.3.7
 Serial: 6447364
 Slot Authentication (9a): nicoo@debian.org