Add cntrl+ pgup pgdown shortcuts to navigate in tabs

[y1111]

like i said in . its easier and more useful.
#1260

and also when u right-click in the tabs it does nothing . it could have a menu like close tabs , close all in the right left etc.

and also how to copy the tab adress ? and url or smt like. , to share a link to the page for ex. or to cite a page in a pare for ex. it could have a "copy link to page" or even "copy citation" standarized.

[kelson42]

@y1111 yes, for the tab shortcuts... but first we should check first if all browsers on win and linux work coherently that way.

But please keep one topic per issue. The other ideas should be treated each in an issue.

[y1111]

all chromium and gecko browsers that i already used work like that .

[kelson42]

https://github.com/kiwix/kiwix-desktop/pull/867/files is interesting