Be more transparent with the status of the WARC creation process

[machawk1]

A user, Zappa Penguin, stated on the Chrome store review:

Too inconsistent to be trusted. For instance, it hangs when trying to WARC this storefront page. It's very opaque, with no way to check status - you click "generate" and it doesn't do anything, either because it's actually generating a WARC or because it's crashed or hung on something, and there's just no telling which possibility is the case. On the bright side, it's not a CLI python script, so... points for that.

The extension ought to provide some way to monitor the status of WARC assembly, auditing, and where it might have failed