Draft: Add hint `x-xfce4-full-with-value` that allows to show summary, body and actions together with a gauge (fixes #4)

This MR fixes #4 (closed). If there is a hint x-xfce4-full-with-value then summary, body and actions are not hidden even with a value hint provided.

For example, the command

gdbus call --session --dest org.freedesktop.Notifications --object-path /org/freedesktop/Notifications --method org.freedesktop.Notifications.Notify "App" 0 "battery" "Summary" "Body" '["Action", "Action"]' '{"value": <30>, "x-xfce4-full-with-value": <1>}' 0

Yields following result:

What do you think about the name of the hint? Maybe you known a better one?

What do you think about the order of items? There are alternative ones, for example, here, this one is proposed: