Improve documentation about shortcuts

[maxcnunes]

Would be good have a page listing all available shortcuts.
The app already has few shortcuts and the ace editor also has some good shortcuts.
I was thinking in keep it simple and just adding a link in the app to a webpage which could be a markdown file in the repository or even a page in the wiki (which we don't have yet).

What do you guys think?

[BornaP]

I agree on adding this! Link to the markdown file sounds good enough, but if you were thinking about creating a wiki page anyway, then that would be a better solution! :)

[maxcnunes]

Ok, so a wiki it will be 😄