Merge branch 'master' of https://github.com/Sigil-Ebook/EpubJSReader

Merge branch 'qt5-qt6'

fix image max-size in two page spread mode

a better fix that uses internal resolveUrl routine

fix toc_controller bug in reader.js converting nav/ncx rel paths to o…

…pf rel

add in contributed icons from BeckyEbook

update README and buildplugin script