Markdown : Display non-formated

[Sirr-Al-Asrar]

Hi,
As a simple syntax for publish on the web, markdown provide an easy formatting but a good visibility too when is not formatted.
Use a keyboard short-cut or a button to switch to formatted or non-formatted display can be consistant with markdown philosophy and it can be great for front-matter usages, or for modify syntax instead of the content, ...

Thanks for the work. This collaborative editor is awesome 🥇

[juliusknorr]

Duplicate of #439 which will not happen any time soon due to the way our collaborative editing is implemented. (see also #323 (comment) for some additional details)

[Sirr-Al-Asrar]

Ok, thanks

[claell]

Duplicate of #123