On long-press on the "Show matched stylesheets rules"
buttons, ignore those from our epub.css/html5.css and
from styletweaks, which may make investigating a book
style simpler without their noise.
Move View html code from ReaderHighlight to a new
dedicated module.
Long-press on an element or its text in the HTML will
show a popup with a list of selectors related to this
element that can be copied to clipboard (to be pasted
in Find or in a Book style tweak).
2 addtional buttons in this popup allow seeing all the
CSS rulesets in all stylesheets that would be matched by
this element, which should make it easier understanding
the publisher stylesheets and using or creating style
tweaks.
