text: Title: Way to get the vertical scroll bar percentage
  Body: ## Expected Behavior
  Expect to get vertical scroll bar percentage
  
  ## Actual Behavior
  Able to scroll down
  Unable to get verticalscrollbar percentage
  So that we can determine scroll bar is 100% scrolled down
  ## Steps to Reproduce the Problem
  
    1.
    2.
    3.
  
  ## Short Example of Code to Demonstrate the Problem
  Currently using get_propeties() method but it doesn`t have info about it
  
  ## Specifications
  
    - Pywinauto version:0.6.8
    - Python version and bitness:3.7.8
    - Platform and OS: uia n 
  ![IMG_20211019_143236](https://user-images.githubusercontent.com/81166452/137878450-1b51ae4b-1a67-48f5-a3b5-0b939f9d07ac.jpg)
  Windows
  