Provide examples for all window position/size setters

[rukai]

• Tested on all platforms changed
• Compilation warnings were addressed
• cargo fmt has been run on this branch
• cargo doc builds successfully
• Added an entry to CHANGELOG.md if knowledge of this change could be valuable to users
• Updated documentation to reflect any user-facing changes, including notes of platform-specific behavior
• Created or updated an example program if it would help users understand this functionality
• Updated feature matrix, if new features were added or implemented

This API is easy to understand once you've seen an example, but figuring it out from just the type signature is really difficult.
So every method with args of <S: Into<Size>> or <P: Into<Position>> should have an example demonstrating how to use it.

I considered putting this documentation just once in Size or Position.
But that would have been strange as we would be documenting how to instantiate a different type on a types documentation page.
And it would be harder to find for the user.

[maroider]

I assume this is ready to be merged now?

[rukai]

from my perspective yes

[madsmtm]

Also from mine, thanks for your work!