Make renderer respect `width` and `height` from query params

[Poitrin]

When calling /renderwindow/preview/?width=426px&height=240px, the query parameters (width, height) have no effect, because they are overridden by the config file, see code:

SPX-GC/routes/routes-application.js

Lines 2106 to 2140 in 3bfa2c8

	function getResolutionFromConfig(cfg, postRequest) {
	// Added in 1.3.0 to get resolution
	// returns CSS values: {width: x, height: y}
	let sizeID = cfg.general.resolution || 'HD';
	let width = '1920px';
	let height = '1080px';
	if (postRequest.width ) { width = postRequest.width }
	if (postRequest.height) { height = postRequest.height }
	switch(sizeID) {
	case '4K':
	width = '3840px'
	height = '2160px'
	break;
	case 'AUTO':
	width = '100vw'
	height = '100vh'
	break;
	default:
	// HD is the default
	width = '1920px'
	height = '1080px'
	break;
	};
	return {
	width: width,
	height: height,
	};
	} // getResolutionFromConfig ended

Based on the existing code, I assume that returning an object with width and height if query parameters are present solves the issue.