Loading / Status Dialog

Hi, just a quick suggestion to add a loading indicator, of some sort.

I've been trying to get Blast Radius to work all day and couldn't figure out why the graph.svg file would hang in my Chrome inspector. It just says "(pending)" for a long while and I thought something had been misconfigured or wasn't working properly.

After finding #25, however, I realized that nothing was wrong, after all, and it was just taking a while for the graph to be generated (~8 minutes), presumably because our Terraform config is relatively large (though, it's really not HUGE by any reasonable standard).

With that said, Blast Radius does not provide any indication that the graph is being generated behind the scenes and I think its very easy for people to assume that it's broken when nothing appears. So, I think the user should be informed about the ongoing render process in some way, if at all possible.

Of course I realize that this project probably doesn't justify a ton of time and expense and that it was created as a sort of proof-of-concept, but, still, I thought it would be useful for me to share my experience and provide the suggestion.

A few other notes:

Refocusing the graph causes another, long, delay, which could probably, also, benefit from a loading indicator. (It also makes me wonder if some data could be cached for performance)
graph.json laggs behind graph.svg, which is also not obvious.

Anyway, thanks for the awesome utility!

28mm / blast-radius

Loading / Status Dialog #29