Add ActionController::UnknownFormat to ignore exceptions

[iguchi1124]

ActionController::UnknownFormat is rescued 406 http response from rails 5.

rails/rails#20666

so, I added this exception to default ignore exceptions. what do you think? @nateberkopec

[nateberkopec]

Hmmm... sometimes I like receiving these because they're usually bad bots that I want to block. I guess I'm not sure.

[iguchi1124]

I don't want to notify this error because this is not a server error.
It has better to make configure in the application's Rave.config.excluded_exceptions if someone want to notify this error for security reasons.

I think this proposal is same as ignoring ActionController::InvalidAuthenticityToken. 💭

[nateberkopec]

Closing in favor of #769, but thanks for opening (otherwise wouldn't have had the idea!)

[iguchi1124]

thanks!