Allow for flipx and flipy

as opposed to flipX and flipY (cammel text)

Author: THEkatinamicrowave

source/funkin/backend/utils/XMLUtil.hx

@@ -143,8 +143,8 @@ class XMLUtil {
 			var graphicSizey:Null<Int> = Std.parseInt(node.att.graphicSizey);
 			if (graphicSizey.isNotNull()) spr.setGraphicSize(0, graphicSizey);
 		}
-		if (node.has.flipX && node.att.flipX == "true") spr.flipX = true;
-		if (node.has.flipY && node.att.flipY == "true") spr.flipY = true;
+		if ((node.has.flipX && node.att.flipX == "true") || (node.has.flipx && node.att.flipx == "true")) spr.flipX = true;
+		if ((node.has.flipY && node.att.flipY == "true") || (node.has.flipy && node.att.flipy == "true")) spr.flipY = true;
 		if (node.has.updateHitbox && node.att.updateHitbox == "true") spr.updateHitbox();
 
 		if (node.has.zoomfactor)