Allow `id_ed25519.pub` key file to be found as default SSH key

[marianschmidt]

RStudio has changed the default generated SSH key to ED25519, which means that also the key file name changed and cannot be found by the default internal cyphr function openssl_find_pubkey. I would suggest to:

• add id_ed25519.pub to the default algorithm to find keys inside the ~\.ssh folder OR
• allow custom key names