How to set app launch window size

[jiangk576]

Description

I wonder how to set launch window size in maui。
When I search for Issues and DIscussion，I found there is no universal way to set launch window size in maui, #2370 ,someone says in windows we can get the window handler first and change window size, but in macOS there is no workaround way.
And I also find #4942 , this work will allow us to set window size to a fixed value while targeting Windows, What about MacOS? I think it's not an uniform solution for maui framework。

Public API Changes

setWindowSize()
setWindowLocation()

Intended Use-Case

I want to show different window size when using multi-window, so I need to set app launch window size。