Add flashcart index script

[chrisdiana]

Added a script to generate a flashcart index file (like in ./example-flashcarts/example/flashcart-index.csv) to allow for adding/updating game libraries without having to manually change the CSV file.

https://github.com/MrBlinky/Arduboy-Python-Utilities/blob/master/example-flashcarts/example/flashcart-index.csv

The script follows this format:

    - Action
    - - Hopper.hex	                # game file
    - - Hopper.png	                # game screen file
    - - Lasers.hex
    - - Lasers.png
    - Adventure
    - - Arena.hex
    - - Arena.png
    - Categories		        # category screens directory
    - - Action.png 	                # category screen file
    - - Adventure.png 		# category screen file
    - arduboy_loader.png 	# title screen
    - flashcart-image.bin 	# flash cart image
    - flashcart-index.csv	        # flash card index directory needed to build image

[chrisdiana]

@MrBlinky was curious if there is any issues with this script. I figured this could replace the one command loader I was using.