Add title pane embedded underline selection color

[basix86]

Suppose this use case with embedded title pane and underline enabled.

UIManager.put("MenuBar.background", new ColorUIResource( Color.BLUE));
UIManager.put("MenuBar.foreground", new ColorUIResource( Color.WHITE));
UIManager.put("TitlePane.embeddedForeground", new ColorUIResource( Color.WHITE));
UIManager.put("TitlePane.background", new ColorUIResource(Color.BLUE));
UIManager.put("TitlePane.foreground", new ColorUIResource(Color.WHITE));
UIManager.put("MenuItem.underlineSelectionColor", new ColorUIResource(Color.BLUE));
UIManager.put("MenuItem.selectionType", "underline");

We need a new key (for example TitlePane.underlineSelectionColor) to have underline WHITE in the TitlePane and BLUE in MenuItem

[DevCharly]

@basix86 thanks for the PR.

I've extended it to also support different underlineSelectionBackground and underlineSelectionHeight for menu bars.

UIManager.put("MenuBar.underlineSelectionColor", Color.white);
UIManager.put("MenuBar.underlineSelectionBackground", Color.red);
UIManager.put("MenuBar.underlineSelectionHeight", 5);