Fix spread layout before layout completes
Fix spread layout before layout completes

Set `data-vivliostyle-page-progression` attribute when the readyState becomes `interactive`.

vivliostyle/vivliostyle.js,vivliostyle/vivliostyle-ui,vivliostyle/vivliostyle-ui,vivliostyle/vivliostyle.js,vivliostyle/vivliostyle-ui,vivliostyle/vivliostyle.js,vivliostyle/vivliostyle-ui,vivliostyle/vivliostyle.js