CSS.supports prevents Codeflask from working in IE11

[marcysutton]

The CSS.supports call in editor.js throws an unrecoverable error in IE11. Lots of people still use IE, and it's a pretty easy change to get it working. I wrapped it in a try...catch block but there might be a more graceful way to do it.

let COLOR;
try {
  COLOR = (CSS.supports('caret-color', '#000')) ? BACKGROUND_COLOR : '#fff';
} catch (e) {
  COLOR = '#fff';
}

[marcysutton]

I should mention the styles are also pretty jacked up on iOS Safari.

[kazzkiq]

I've added an utils function that handles it properly, even for browsers that still doesn't have CSS.