function reExtnameWindows() {
	return /^(?:[a-zA-Z]:|[\\\/]{2}[^\\\/]+[\\\/]+[^\\\/]+|)(?:[\\\/]|)(?:[\s\S]*?)(?:(?:\.{1,2}|[^\\\/]+?|)(\.[^.\/\\]*|))(?:[\\\/]*)$/; // eslint-disable-line no-useless-escape
}
Returns a regular expression to capture a Windows filename extension.

@returns {RegExp} regular expression

@example
var RE_EXTNAME_WINDOWS = reExtnameWindows();
var ext = RE_EXTNAME_WINDOWS.exec( 'index.js' )[ 1 ];
// returns '.js'