Add category parameter to DangerXcodeSummary::Result

[yhkaplan]

I would like to improve the ergonomics of Result by adding a parameter called type or category that specifies whether it's a build error, failing test, warning, etc. This would make setting the ignored_results block much easier. What do you think? If you like the idea, I'll submit a PR!

[diogot]

I like the idea, feel free to submit a PR.
Thanks