Add a "Mountain" type to the ViewElement enumeration.

src/main/java/view/FirefighterGrid.java

@@ -96,4 +96,5 @@ public class FirefighterGrid extends Canvas implements Grid<ViewElement>{
     private void clearBox(int row, int column){
         getGraphicsContext2D().clearRect(column * boxWidth,row * boxHeight, boxWidth, boxHeight);
     }
+
 }
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