ready callback doesn't fire if an integration is blocked or fails to load

[rawberg]

If an integration fails to load or is blocked by an ad blocker then the ready callback never fires. The ready function should execute even if one or more integrations fail to load.

[tejasmanohar]

Currently, the ready function is all or nothing (just as documented). That said, I agree that the ability to denote when a certain integration has loaded and record failures is important to many applications, but since this has already been pointed out in #409, I'll close this issue in favor of that.