Add read me content to the (settings page) app

[mvaneijgen]

Just loaded the app onto my Boox note air 3 and looking great. Distraction free note taking (would love to even have the top bar hidden while taking notes) for the win!

I'm not going to remember all the gestures (and when in the future their going to be probably more) I would love a little read me inside the app with in theory the readme from this repo, so that I can reference its functions while inside the app. I usually use my device when there is no internet connection, but even with an internet connection having the functions of the app in the app would be nice.

You could even draw a "this is how the app works" default note and load that by default when you install the app. Then users can keep or delete that page when they see fit.

Keep up the good work!