unexpected click behavior in gallery/document view

[r10s]

clicking eg. a PDF when in gallery/document-view, the experience is different from clicking the same PDF in the chat:

• in the chat, the PDF viewer is opened, a right-click offers an option to export the PDF - everyhing's okay here :)
• in gallery/document view, there is an unexpected and distinction between icon-image and icon-title: the PDF viewer only opened when clicking the icon-image - when clicking the icon-title export is done.

this is totally unexpected - first, i thought, opening the viewer is not supported from the gallery :) then i thought there is a random bug :D

we should change this so that the primary action (opening the viewer) is not related to the position the user clicks - this is also what most other UIs are doing here, including eg. windows explorer, mac finder and Delta Chat in the chat view.

a right-click can offer export and other things then. that also matches better to the gallery/image view.