[microflash]

There's also a generic directive proposal[1] that enables admonitions, YouTube embeds, etc. With remark[2] plugins, markdown can be as extensible as you may need. Here's a sample plugin for admonitions[3] by yours truly.

[1]. https://talk.commonmark.org/t/generic-directives-plugins-syn...

[2]. https://github.com/remarkjs/remark

[3]. https://github.com/Microflash/remark-callout-directives