Add option to change the colors of the tiers and image export option

[AtomicLugia]

This tier list maker is pretty good so far, all it needs is a button to save the tier list as image and a way to change the colors of the tiers.

[sarantula]

A image export would be great. I just use the screenshot tool but still would be a nice QOL feature.
Also just wanna say, I love this tier maker so much. I hate having to spend time resizing and compressing images to upload to other sites, this is a simple copy paste and does the work for me. So much easier to use. Thank you so much for making it.

[silverweed]

Thanks for the feedback! I hope I can do something about the requested features after I'm back from my Xmas break.