[docs-theme] Regression in markdown rendering

[adidahiya]

@blueprintjs/docs-theme 3.2.0

caused by #3482. Documentation markdown inside HTML tags is no longer being rendered correctly.

Actual behavior:

Expected behavior:

[adidahiya]

This seems to be a markedjs bug: markedjs/marked#985

We might switch to another markdown rendering library at some point, but for now I'm going to manually fix the "mixed" content using newlines between HTML tags and markdown to get the rendering back to what we expect.

VSCode's syntax highlighting for markdown suggests that this is a reasonable approach as well (I get the right highlighting for markdown inside HTML when I use newlines)...