doc(readme): background transparent on iOS when StatusBarOverlaysWebView is true

[GitToTheHub]

Platforms affected

iOS

Motivation and Context

The documentation made not clear, that the status bar background color is transparent on iOS when StatusBarOverlaysWebView is set to true and cannot be changed by StatusBarBackgroundColor.

I looked in the code and the status bar background view is removed if StatusBarOverlaysWebView is true, which is the default:

cordova-plugin-statusbar/src/ios/CDVStatusBar.m

Lines 230 to 232 in 70f4445

	if (statusBarOverlaysWebView) {
	[_statusBarBackgroundView removeFromSuperview];

Description

Testing

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary