Provide SARIF output

[mjpieters]

Please add support for outputting SARIF (Static Analysis Results Interchange Format) information.

This would help integrate nitpick into other tools, as SARIF is a widely supported standard format for code analysers including linters like nitpick. E.g.:

• GitHub accepts SARIF reports and will show information inline
• MegaLinter will support SARIF on the next version

[andreoliwa]

Thanks for yet this suggestion.
I haven't heard of this SARIF format before, but it looks interesting for nitpick check, I assume.

• For me, it's always good when open-source tools work together like you're doing with feat: Add MegaLinter plugin #476.
• There is also an issue for Prospector: Include nitpick in prospector prospector-dev/prospector#441

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(food for thought, maybe for a separate issue)

For all this integration to look great, the current output should be better formatted (AKA revamped).
E.g. standardise error messages, remove duplicates, renumber (there is a draft card on the Roadmap, but I've yet to think and write a decent issue with details).

Also, line references are not returned by Nitpick.
It might be tricky to do that, I haven't thought much about it.

Right now, each Nitpick plugin (TOML/YAML/JSON/INI) has its own way of comparing dicts and applying a diff on the original file.

To work as a proper linter (like flake8 or pylint), I would have to find and return the line number of each line-to-be-modified.
I don't think the packages I use provide such thing, e.g.: tomlkit and ruamel.yaml.