247: Standardize image size in posts.

Few explanations:

1. I used @AppStorage("screenWidth") var screenWidth: Double = 0 because we want to have all images with one width, as we can get different results while we scroll it was not safety to relay on size of screen.
2. I used imageHeight = (proxy.size.height < 400 || proxy.size.height > 600) ? 500 : proxy.size.height to give us a bit of space how tall image can be, it also can improve quality and show more objects or safe proportions if image height in range 400...600 points