To make the certificate details more efficient to reach for keyboard only users, we should add a default keyboard shortcut.
We want to use Enter as the default key for opening the details of a focused certificate list line.
Reasoning: It is used in other applications for this purpose. And Enter in Kleopatra currently only has an effect in a window where a default button is defined and the certificate list has no buttons.
Currently the details can be reached with the keyboard with Shift + F10 to open the context menu when the focus is on the certificate and then choosing the details entry there. Which is the last entry for the vsd 3.x versions and the first one for Gpg4win 5.x.