add the LICENSE and put together a basic README
Created by: mmahmoudian
I tried to add enough explanation about the LICENSE file as possible considering the current state of the situation.
Also regarding the README, I basically copied text from F-droid and image from the Playstore page of the app. I couldn't find any licensing about the images there, and I assume there were uploaded by Sergey Solovyev, and therefore logically should be subjected to the same license as the app.