Generate Confluence macro for an expand block
confl_macro_expand(title, body)
| title | defines the text that appears next to the expand/collapse icon | 
|---|---|
| body | this HTML content will be visible when someone clicks the macro title | 
HTML as string
content needs to be HTML, so look at commonmark::markdown_html, pander::pander and eg xtable for doing the conversion before passing to confluence_expand
https://confluence.atlassian.com/doc/expand-macro-223222352.html
if (FALSE) { confl_macro_expand( 'Example block', commonmark::markdown_html(pander::pander_return(list(a = list(b = 4), c = 2)))) }