Added keybindings doc

[imolein]

I read a couple of times that some people wanted a documentation of the keybindings. I wrote them all together in a Zim Wiki page for personal use some weeks ago, which I have now converted to Markdown. It's not very pretty, but I think it is a start. :)

[SwissalpS]

Nice layout. Since everything is dynamic and reconfigurable, I've been working on a dynamically created list.

In one project you may have keybindings set to do something different than in another project.

[imolein]

Nice! I had already thought about creating a documentation plugin myself. Nice to see that someone is already working on it :)

[ghost]

Looks good. Why isn't it merged yet?