Allow fallback to hosted js files without cdn

[ofbeaton]

Tried to use graphiql on an intranet without an internet connection, horrible experience, everything is loaded from cdn.

Similar issues in other flavours of graphiql, seems like I'm not the only one having this issue.
expo/koa-graphiql#1

Could we have a fallback where if the cdn fails to load the files it loads a local copy?

[dolphin278]

Right now jsdelivr went down, suffering from DDoS attack so GraphiQL became completely unavailable :(

https://twitter.com/jsDelivr/status/732245796066852864

[asiandrummer]

Good suggestion @ofbeaton - a fallback local copy makes sense to me.

[ofbeaton]

Perhaps something similar to what the initializr template recommends for jquery?

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="js/vendor/jquery.min.js') }}"><\/script>')</script>

[asiandrummer]

Sorry I've been super late with this - 236591 adds the fallback to the local copies. Thanks for the suggestion!