README file list example has low contrast

The GIF in use on the LittlevGL README has a very low contrast for the left list:

Maybe it’s just my monitor, but I find it hard to tell when an item is selected. Maybe we should pick a different theme for the left?

True.

I’ve updated the night theme. It looks like this now:
list_theme_example

What do you think?

@kisvegabor Much better!