detect end of a window-resize

[<c buhtz posteo jp>]

There are some questions and solutions in the web how to detect the
ending of a window-resize. I mean the situation when the user drags the
border of a window with its mouse and change the size that way. This
causes hundreds of resize-events (e.g. 'size-allocate').

But most of the time only the first and the last event is important for
us.

Depending on some hints, comments from you and other communities I
created a PyGObject/Python3 example solution on StackOverflow.

https://stackoverflow.com/a/54709415/4865723

It would be nice if you as core devs and professionals could check it
out and maybe improve it.