Import shared definitions from `/example`, and remove numerous forms of redundant code, including compatibility definitions. Also, fix a few minor issues with dialogs being too small in the test suites.
Add shared code between the examples, to reduce the amount of
boilerplate used in each example. Includes shared colors, Qt5/Qt6 compat
definitions, argparsers, and app startup/exec code.
Added an example PyQt6 application with a workaround to attempt to fix
the placeholder text color issues, which further supports the idea that
it is a Qt bug, and not a stylesheet issue.
Using `QtGui.QPalette.ColorRole.PlaceholderText`, we are able to modify
the placeholder text color in Qt5, but not in Qt6.
Closes#41.
Closes#44.
Alex Huszagh