FIX: fix/update mupdf backend

FIX: check all pages converted via number of image files

FEAT: free selection mode

Add pymupdf-epc install command

Initial commit cleaned up (fast) version

Add funding info

Fix mode-line page indicator

Update/extend README

Improve 'create-imenu' function (extracting page numbers)

Update

Add pymupdf backend

Fix namespaces and tmp directory

README: add minimal usage instructions

Extend djvu annotations (line and text) support

README: add installation instructions (and some more info)