previewer: pdfjs plugin addition

* Adds pdfjs previewer.

Signed-off-by: Adrian Pawel Baran <adrian.pawel.baran@cern.ch>
133:1: F999 redefinition of unused 'compile_text' from line 114
140:1: F999 redefinition of unused 'compile_binary' from line 121
146:1: F999 redefinition of unused 'compile_largebinary' from line 127