history navigation doesnt work with mouse forward and back

[voidplayer]

Godot version: 3.2.1.stable

OS/device including version: debian/testing

Issue description: Mouses have a couple of buttons that emulates alt + left and alt + right. They are used to ease the navigation. Since you have to grab it to go to the help (ctrl + click) its very annoying that they dont work because you cant do a quick peak of the help

Steps to reproduce: ctrl click on a help item. Press back or forward button. It does neither

Minimal reproduction project:

[Calinou]

This is implemented by #36910. I'm pretty sure I've seen other issues about this but I can't find them right now.

[KoBeWi]

Also implemented by #32071. There were issues about binding these buttons for history, but none of them is directly about scripts.

[Calinou]

Closing in favor of godotengine/godot-proposals#954, as feature proposals are now tracked in the Godot proposals repository.