Improve M3 color scheme parsing

[braniii]

So far, trale parses the accent color and creates a color scheme from it. Using secondary color palettes, the accent color and background color do not match. Using the following method, it should be able to parse the whole color palette of the user to integrate better.

PS: Reading material-foundation/flutter-packages#599 it seems that the solution is to migrate to https://pub.dev/packages/dynamic_system_colors until the package dynamic_color is upgraded.