sean watters

Resolve these same issues from the React Web project: https://github.com/chartiful/react-charts/issues?q=is%3Aissue+is%3Aclosed

fix(example): upgrades window customization example from deprecated cocoa to objc2-app-kit

3

#### Description - What does this PR change? Give us a brief description. > Updates docs for changing window color on MacOS to use objc2-app-kit instead of deprecated cocoa crate.