Warn you that your edits will be lost

[kzeitz]

I was using the antlr4-lab and noticed an issue, so I reflexively clicked the 'issues' link and inadvertently lost some edits.

Perhaps the links could open another tab by default, or at least prompt you that you will be lose any changes you've made.

[parrt]

Excellent point. Yeah I'm worried about that as well. Not sure how to handle that but perhaps we can simply detect when you were going to move away from the "app" with a bit of JavaScript. We can then pop up a dialog box warning you. I think Jupyter notebooks and things like that work like that.