v2.3.7 Release

This release removes the dependency on PySimpleGUI constants for theming the custom titlebars, so PySimpleGUI 4.60.4 Released 10-Oct-2022 no longer brings up an import error. Also, Scrollbars now work properly with the element.ttk_style_name attribute, in addition to multiple readability refactors and progress towards fixing multiple, more evasive bugs.