Markdown Re-Render Button

Hello, I hope this is the correct repository for this request.

I noticed that when working with TeX, especially with global defs and commands (props to HackMD for supporting this, it's the reason I switched from StackEdit), sometimes the rendering gets stuck, i.e. it refuses to render an equation although it's formatted correctly. I don't have a perfect scenario for replication, but this often happens when you change global definitions which are referenced later in the file. In this case, reloading the page settles it. I understand that this is a subtle issue to fix, but think it would be cool to have a small button which re-renders the markdown from the beginning, so you can avoid the full reload!