Ability to generate and save a new password

[pbkhrv]

Simplest workflow:

• User enters "kp new entry title"
• Ext displays search results and "Generate and save password / Create 'new entry title'"
• User selects "Generate..." and presses Enter
• Ext runs keepassxc-cli add -g database_path "new entry title"
• Ext copies the new password to the clipboard

(Password length and generation options can be made configurable, passed as CLI options)

One downside of this approach is that there's not a straightforward way to specify username or URL for the new entry. There might be a ulauncher-centric solution for that, need to think about it.