Support "one sentence per line" in MD content

[karenzone]

We've used the "one sentence per line" asciidoc guideline with great success in our classic docs. This approach brings lots of benefits, and makes GitHub doc reviews and suggestions much more straightforward, easier to understand, and easier to implement.

From @bmorelli25: This is currently not supported in V3. However the commonmark spec does support (and recommend) this feature.

[shainaraskas]

#510

[bmorelli25]

Added in #510.