Opening the class for customisation

[mcomissocdc]

Hey Franco, thanks for writing this!

I've added it to our Danger configuration, and I was looking into customising some features.

I have 2 problems at the moment:

• that the filter function (Result) -> Bool does not give me the full context of the overall results
• the summary does not expose a readable variable for warnings/errors either (this prevents me from creating my own warnings array to then Danger.warn() manually).

Example:
Compact these multiple warnings into a single message with an overview of the lines impacted by the same error/warning.

/path/to/file.swift#L123 Description of the issue
/path/to/file.swift#L234 Description of the issue
/path/to/file.swift#L345 Description of the issue

/path/to/file.swift#L123 + L234, L345: Description of the issue

Happy to write a PR about it, if it's aligned with the scope of the plugin.