Add SSH-key item type

[quexten]

Creating this to track upstream changes for the new ssh-key item type:
bitwarden/server#4575

Note: The creation of ssh keys is gated behind a feature flag, so clients will not be able to post the un-supported cipher to an old version, or to vaultwarden, while not implemented into that vaultwarden server yet.

Eventually, when the feature flag is removed, creation will be gated behind a minimum server version.

Feel free to ping me if there is anything needed from upstream.

[quexten]

Whoops, noticed this is a duplicate. Sorry about that.