Add configuration options that allow (partial) enforcement of the semantic line breaks specification

[thomaseizinger]

I've recently come across https://sembr.org/ and I am a big fan so far.

In our markdown documents, we are already trying to follow the "one sentence per line" rule. This makes our Git diffs more readable because natural language tends to be edited on a sentence basis (i.e. rewrite a single sentence, split it in two, merge two into one, etc).

This behaviour is captured in requirement 4 of sembr.

I haven't looked into the parser and formatter yet but it would be amazing if dprint would make it easy to have markdown documents follow sembr.