site-builder only checks against lower-case "jpg"

[california444]

HI,

I found one issue with site-builder. It only checks against lower-case "jpg" and doesn't check png at all. Although the resize function tales care of png.
Changing line 54 index.js of site-builder to
return object.startsWith(album + "/") && (object.toLowerCase().endsWith('.jpg') || object.toLowerCase().endsWith('.png'));
fixes the issue.

Thanks for the great work.
Best Roman