Ignore spread on items when impossible

[wooorm]

Subject of the feature

Markdown allows lists to be loose or tight. The difference is that <p> tags are output on paragraphs in list items if its parent (i.e., item) is spread, or its parent (i.e., list) is spread.

Problem

Whether lists / list items are loose is stored on nodes.
But there are certain constructs not possible when tight: such as two adjacent paragraphs. Or indented code after a paragraph. Or a setext heading after a paragraph.
These combinations could be injected into the syntax tree by utilities/plugins.

Expected behavior

to-markdown should ignore spread on listItem if it can’t make sense.

Alternatives

Utilities/plugins could be required to fix this, but that’s rather hard, and userland.