Add support for ecdsa-sk and ed25519-sk

This issue is similar to #17 and should be fixable in the same way.

The new line should be :
```php
protected $format = '/^([-[:alnum:]=",.]+\s+)?(disabled-)?(ssh-(dss|rsa|ed25519|ed25519-sk)|ecdsa-(sha2-nistp\d{3}|sk))\s+([[:alnum:]+\/.=]+)(\s+([[:graph:][:space:]]+))?\s*$/';
```