version 1.3.10

• added FlatLaf - Flat Look and Feel (current version 2.4)
  • FlatLaf is a modern open-source cross-platform Look and Feel for
    Java Swing desktop applications.
    https://www.formdev.com/flatlaf
    https://github.com/JFormDesigner/FlatLaf
• added dark mode (light-on-dark color scheme)
  • to activate it, please edit the file appstart.properties
    and remove the "#" from the line that ends in FlatDarkLaf or FlatDarculaLaf