Adjust pdfviewer theming based on accessibility usersetting

[szaimen]

Hi,

The following PR will probably soon be merged: mozilla/pdf.js#11077 which will bring theming support and a light and dark mode, afaik.

So I guess it would be great if the theming could be automatically toggled depending on the accessibility usersetting (dark/normal).

Cheers!

[skjnldsv]

Yep, we need to adapt it a bit. We're discussing wether implement it on top of server styling (overriding both server and pdf.js css, or just not ship any server styling and only adapt the default pdf.js styling) see #202

[szaimen]

This could maybe make use of nextcloud/viewer#1051 like text is now doing nextcloud/text#1907