Doc

@chanhuiwah @kenlam296 @RonaldPark

help to write the doc in /doc folders, view in https://www.quantr.foundation/docs/?project=Quantr+Logic&url=https%3A%2F%2Fgitlab.com%2Fquantr%2Feda%2Fquantr-logic%2Fraw%2Fmaster%2Fdoc%2FIntroduction.MD&docPath=Introduction.MD