Add footnotes module

The footnotes module adds CSS parsing for:

@footnote {
    float: bottom;
}

Only bottom is supported for now, per https://www.w3.org/TR/css-gcpm-3/#creating-footnotes, but should be extensible enough to support left / right / top eventually.

Float footnote will move an element out of the text flow and into a the .pagedjs_footnote_area div, leaving behind a footnote-call span.

span.footnote { 
    float: footnote;
}
.footnote::footnote-call {
    color: red;
}
        
.footnote::footnote-marker {
    color: blue;
}

• Notes that can't fit on the page without pushing the note call off-screen will push the note call to the next page using a parallel break token just for the footnote area
• Handles footnote-policy, basic footnote-display inline support
• Adds clonePage method to create a new page with the same styles as the previous one
• Adds afterOverflowRemoved handler to get the content removed on overflow
• Implements multiple counter resets on elements and atpage
• Fixes counter reset increment for pages: https://gitlab.pagedmedia.org/tools/pagedjs/issues/91
• Fixes counter reset setting for pages: https://gitlab.pagedmedia.org/tools/pagedjs/merge_requests/88
• Update dependancies, fixs specs for latest Chrome versions

This is all based on the great notes script by @JulieBlanc!