Ensure paragraph splits are retained in long descriptions

[dgkf]

In general, splits between paragraphs, and between formatted markdown sections is a little rough.

For example, using DescTools's Mode.Rd as an example (because it has huge blocks of text in its description), the formatting merges many of the paragraphs together.

For comparison, see how tools::Rd2txt handles the descriptions, which retains clear paragraph separation.

[maksymiuks]

Closing as it was solved by #20