Is your feature request related to a problem? Please describe.
When creating demo videos of Rerun I want the screen to have a specific aspect ration (different depending on where the video will be shared). Right now I have to fiddle a lot by hand to get it to the right size.

Describe the solution you'd like
I want to be able to explicitly configure the screen resolution of Rerun. One option would be as a command line argument like:

python -m rerun --window-size 1500x900 

Describe alternatives you've considered
Another alternative could be to somehow expose the window size as a blueprint option. This would be more consistent of how we want to use it in the future.