feat: Add keymap descriptions
Let me know if you're happy with the descriptions I added, here's a screenshot of the final result:

Thanks @rafamadriz for putting this together.
Just one thing, isn't it better to start the description with Toggle comment ... for toggle mappings. Thoughts?
@numToStr I thought about that, but I felt that it was better to have a naming convention where you first start with name/label -> action. So for example, you have Comment and Uncomment as names/labels and then action to happen. But besides that, I don't really have a good reason to not do it the other way, just let me know if you want me to change it
@rafamadriz I agree with you. Please review the requested changes then we could go ahead with merging this :)