#796 Use native window decorations

[Anonymous]

Originally created by: eug3nix

Pgmanage uses custom window header and buttons. This is especially noticeable on Mac where native window controls are on the left and PgManage has them on the right with a totally different visual style.

Potentially we might want to switch to native window decorations to match OS look and feel.
As I can see this is controlled via frame option: https://nwjs.readthedocs.io/en/nw28/References/Manifest%20Format/#frame