Add support for getting real canvas dimensions

In stretched mode the canvas dimensions are the stretched dimensions, so
add method that will return normal game dimensions in case stretched
mode is enabled and we are not in resizeable mode.

Signed-off-by: Tomas Slusny <slusnucky@gmail.com>

runelite-api/src/main/java/net/runelite/api/Client.java

@@ -331,6 +331,8 @@ public interface Client extends GameEngine
 
 	Dimension getStretchedDimensions();
 
+	Dimension getRealDimensions();
+
 	/**
 	 * Changes world. Works only on login screen
 	 * @param world world

runelite-mixins/src/main/java/net/runelite/mixins/StretchedFixedModeMixin.java

@@ -85,6 +85,18 @@ public abstract class StretchedFixedModeMixin implements RSClient
 		cachedStretchedDimensions = null;
 	}
 
+	@Inject
+	@Override
+	public Dimension getRealDimensions()
+	{
+		if (isStretchedEnabled() && !isResized())
+		{
+			return Constants.GAME_FIXED_SIZE;
+		}
+
+		return getCanvas().getSize();
+	}
+
 	@Inject
 	@Override
 	public Dimension getStretchedDimensions()