feat: add --max-consecutive-empty-lines setting

[stigh]

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Resolves https://github.com/pseewald/fprettify/issues/164.

This does not contain any tests, so is currently only intended as a proposal. This solves only one of the several limits with fprettify I need to solve to be able to define the code standard we use.

I can also add that I have a couple of other feature branches in the works at https://github.com/stigh/fprettify, which are cherry-picked into a development branch which hopefully will work towards the code standard we use.

If I get some kind of indication that this project has a working PR approval process, I intend to put in the extra effort to add the tests required, and the same with the other feature branches I have.