We're currently using 2 features not supported by IE which is breaking the UI:

• HTMLImageElement.decode() (in init.js)
• The IntersectionObserver (various uses)

We have a few options for resolving this:

1. Polyfill the decode function and the IntersectionObserver. This is ideal because it allows us to write one set of code for all browsers.
2. Add some conditional logic to handle things differently if these modules aren't supported
3. Make IE fall back on the PHP UI

I propose we do 2 while working on 1.