Show dialog to confirm if user cancels modification

[cintek]

In the current situation if a user clicks on Cancel on a modify page the wiki just returns to the previous page. All new changes are gone. It would prevent frustration if the wiki would show a confirmation dialog before it really returns to the previous page.

[UlrichB22]

Agree to add a confirmation dialog.
Do you want to create a corresponding solution?

[wagner-intevation]

Either @cintek or I will probably write a PR for this, yes.

[wagner-intevation]

Can a solution for this issue be a core feature for all themes (in the templates), or should it be implemented in the theme? If the latter, we would add it to the focus theme.

[UlrichB22]

If possible, I would prefer a general solution for all themes.