fix: Workaround for Chromium problem of inconsistent screen and print layout
fix: Workaround for Chromium problem of inconsistent screen and print layout

Fixes #758
Fixes #793

Chromium currently uses legacy engine for multicol and print
and uses new engine (LayoutNG) for non-multicol screen,
so we need to use multicol to match screen and print layouts.

This workaround will be unnecessary when the Chromium issue is resolved:
https://bugs.chromium.org/p/chromium/issues/detail?id=829028

vivliostyle/vivliostyle.js,vivliostyle/vivliostyle.js,vivliostyle/vivliostyle.js,vivliostyle/vivliostyle.js