Add ssh-keys interface

[fabius85]

As title says, it would be useful to add the ability to access SSH private keys instead of having to copy them to a dir accessible by FileZilla snap.
https://docs.snapcraft.io/the-ssh-keys-interface/7917

[brlin-tw]

I've published the snap with the ssh-keys plug to the edge channel, however, it appears that snapd doesn't properly expose the host's ssh-agent socket so that even the plug is available password-less login is still not working.

Note that the ssh-keys interface is not autoconnected by default.

[fabius85]

Refreshed to edge channel:
sudo snap refresh filezilla --edge
connected filezilla to ssh-keys plug interface:
sudo snap connect filezilla:ssh-keys
changed path to key file in Site Manager:
/home/myusername/.ssh/id_rsa_myserver
and it seems to be working fine!

Next step i'll be waiting for is conversion to classic confinement, so i dont have to bind mount /var/www to my home directory, but i see it's yet on your "Remaining Tasks" list so i'll just be patient.

Thanks again!