pdfviewer: link rendering and interaction

[ghrimx]

Link in PDF should be highlighted and the viewer should jump to the target of the link.

QPdfView does recognize the link on the first page and areas above the link can be clicked. However, the painted areas do not match the link location and on resizing or jumping to another page these hidden areas remains and links on other pages are not rendered.

To paint rectangle on links, one must know the coordinates of the widget rendering PDF pages in the Qscrollarea which change with the scroll and zoom.

Temporary action: mousePressEvent of QPdfView has been reimplemented to disable link interaction with the mouse and avoid unwanted behaviour. (see pdfviewer.py)

[ghrimx]

A custom pdf viewer is in development (check my other repo PyMuPDF4QT)