Pattern library does not load CSS or JavaScript in IE11

[helenb]

Issue Summary

If you view the pattern library in IE11 (tested with browserstack) it does not load the CSS and JS. The console is reporting a syntax error

Steps to Reproduce

1. Open a new session of IE11 in Browserstack
2. Visit a pattern library page

Any other relevant information. For example, why do you consider this a bug and what did you expect to happen instead?

Technical details

Tested on wagtail-kit which is using pattern library version 0.3.0
Tested on action for children which is using pattern library version 0.5.0

The console reports a syntax error but it is hard to see what this is in the compiled and compressed code:

[zerolab]

I think it is high time we stopped supporting IE11, no?

[thibaudcolas]

PR to fully remove support: #162

We still have a lot of projects with IE11 support targets, so I think it’s important individual patterns can still be rendered correctly in IE11, but the pattern library UI doesn’t have to support it.