Add support for non-biometric unlock

[mrjones2014]

I don't think this plugin will work currently without biometric unlock enabled for the CLI because the CLI will ask for a password.

In that case we would need to have some sort of password input (maybe via vim.ui.input() but ideally it would be a concealed field, so maybe we can do some trickery with a custom input, saving the entered characters to a Lua string internally, but rendering the chars as ******, and then pipe it to stdin of the CLI process somehow.

[mrjones2014]

supported since 4f80a24