add .panzoom-container class to width declaration

[nick3white]

Same as https://github.com/omeka-s-themes/papers/pull/30

This is an issue with the papers theme css, so, as the default theme, the issue appears in the Scripto css as well.

On a transcription edit page, in a full-width window (ie width > 600px) , using the horizontal layout, the page image is not displaying.

I don't know exactly why this is happening, but the details may not actually matter. I'll go into my theory below, but, the PR basically provides the same width value to the .panzoom-container that the #panzoom-container has.

I think what's happening is, when using external images (ie IIIF) with Omeka, the isRenderableImage() check is falsey, and so instead of "actual panzoom" loading, a IIIF viewer loads instead. The result is that the div in the wikitext-flex container, next to the textarea-flex, has a class of panzoom-container, but not the id of panzoom-container. However, in the css, the width is provided to the id, not the class. So this PR just adds the class.

This problem exists in the Scripto code as well, since the css is replicated there. I'll put a PR in for that too, but it's the same thing.

(I can provide a real-life instance of the problem, but the project is far from ready for the public, so I'd prefer to share that privately if that's ok.)

Here's a picture.

[jimsafley]

I believe the problem will be resolved in an upcoming release. This commit likely fixes it. You could pull from master and try it out yourself.

[nick3white]

Yes! That solved it.