Ability to hide viewport

**Is your feature request related to a problem? Please describe.**
I want my application to be able to minimize to the system tray using [pystray](https://pypi.org/project/pystray/) library.

**Describe the solution you'd like**
To do this, I need to hide the viewport in some way.
It would be nice to have a function dpg.set_viewport_visible(bool)

**Describe alternatives you've considered**
[PySide6](https://doc.qt.io/qtforpython-6/index.html) has a [.hide()](https://doc.qt.io/qtforpython-6/PySide6/QtGui/QWindow.html#PySide6.QtGui.QWindow.hide) method.