Write in Markdown (no GUI)

I write in Markdown. I use **bold** and _italics_ by default and if I need a smaller heading I use ## Heading. It'd be nice if those things changed formatting as I typed. I don't want them removed from my document I want to see it so it's there on export but seeing the actual formatting as I type is nice. [Stack Edit](https://stackedit.io/editor#) does it nicely. I'm talking about the text editor box not the preview just so we are clear on that as an example