[FR] Use NativeMessaging for KeePassXC integration

[DominiqueSite]

Electronmail could integrate with KeePassXC the same way the KeePassXC browser extension works. This would greatly ease the setup on new devices; as it would reduce the task to just connecting to the database, instead of manually copying and pasting credentials for – depending on the user – potentially dozens of accounts.

Some users might not want to enable browser integration in the KeePassXC database depending on their threat model, but as long as Electronmail offers to encrypt the host key (unlike browsers, which to my knowledge just store it in plaintext somewhere; see also keepassxreboot/keepassxc#4802), I think the associated risks can be minimized.