Currently an image with a transparent background is rendered with a white background.
This looks weird and is not the expected behavior when a transparent image is used.
With this change the browserWindow is set to transparent, so that the background is not rendered.
If adoptors want a white background they can simply use an image with a white background (or any other color).
Part of #13410
How to test
Start the example electron application and observe that the splash screen image no longer has a white background.
Follow-ups
Review checklist
[x] As an author, I have thoroughly tested my changes and carefully followed the review guidelines
What it does
Currently an image with a transparent background is rendered with a white background.
This looks weird and is not the expected behavior when a transparent image is used.
With this change the browserWindow is set to transparent, so that the background is not rendered.
If adoptors want a white background they can simply use an image with a white background (or any other color).
Part of #13410
How to test
Start the example electron application and observe that the splash screen image no longer has a white background.
Follow-ups
Review checklist
Reminder for reviewers