[Enhancement] PySimpleGUI-TK Ability to force window focus

When running multiple windows, serially where one is closed before another open, on Windows,
new windows do not receive focus after the first window. Only the initial window is given focus after creation.

Where is a workaround available. Use this when you create your window:

   window.TKroot.focus_force()         # Force this window to have focus

   window.Element('-FIRST-INPUT-FIELD-KEY').SetFocus()   # Force this Element to have focus

This will focus the window and move the cursor to the indicated Element.

Comece reproduzindo o comportamento do Windows com janelas PySimpleGUI-TK criadas em série e, em seguida, leia os pontos de entrada de focus existentes indicados no issue: window.TKroot.focus_force() e Element('-FIRST-INPUT-FIELD-KEY').SetFocus(). Considera-se concluído quando as janelas recém-criadas recebem focus de forma consistente sem exigir este workaround, enquanto o elemento indicado ainda pode receber focus do cursor.