Adds a new AnchoredBox component that is functionally a clone of the "saving error" notifications, but drops a lot of the JS in favor of the new (chrome-only!) CSS Anchor Positioning API. In subsequent commits, either alternate styling or a polyfill will be added non-supported browsers.
The box contains a few inputs that modify the CSS applied to `.pages`, most critically a "start on right" toggle for the Facing Pages mode.
This was previously in the .pageInfo widget, probably not for any good reason, but I'm moving it to the popups div for probably not a good reason.
It's used to get the parent .pane div, and pull its `height` value which is then passed to the `.brewRenderer` div to set the height.
I tried alternate methods that would make this obsolete (CSS methods mostly), but due to some complexity am just ditching those alternatives and popping this sucker into `.popups` for now.
handleScroll is replaced by getCurrentPage(), which effectively does the same thing. The math is slightly different, though very similar, and result seems to be the same.
Make it so that if a user enters a page number higher than the total page count, it jumps them to last page. if lower than 1, it jumps them to first page.
putting the `pageInput - 1` modifier in the `scrollToPage` method allows for more understandable button function ('back button' is `- 1` and 'forward button' is `+ 1`).
Moved onChange handler function to a component method and simplified it a smidge.
Must use parseInt now because the input type will change to 'text' rather than 'number'
The website UI should stay out of the iframe if possible. Otherwise, users can style the UI on their brew which may or may not be a pain, and it's simple enough to avoid it.
The makeZoom function is redundant if we just insert the style a little further down when the `.pages` div is initialized, as a `style` attribute on the tag.
