Added test for cuboid surface area

Author: kvadrik

src/test/java/com/thealgorithms/maths/AreaTest.java

@@ -16,6 +16,10 @@ void testSurfaceAreaCube() {
         assertEquals(6.0, Area.surfaceAreaCube(1));
     }
 
+    @Test
+    void testSurfaceAreaCuboid() {
+        assertEquals(214.0, Area.surfaceAreaCuboid(5, 6, 7));
+
     @Test
     void testSurfaceAreaSphere() {
         assertEquals(12.566370614359172, Area.surfaceAreaSphere(1));