Added surface area calculation for pyramid

Author: ShailenN1

src/main/java/com/thealgorithms/maths/Area.java

@@ -78,10 +78,10 @@ public static double surfaceAreaSphere(final double radius) {
      */
     public static double surfaceAreaPyramid(final double sideLength, final double slantHeight) {
         if (sideLength <= 0) {
-            throw new IllegalArgumentException("");
+            throw new IllegalArgumentException("Must be a positive sideLength");
         }
         if (slantHeight <= 0) {
-            throw new IllegalArgumentException("slant height must be greater than 0");
+            throw new IllegalArgumentException("Must be a positive slantHeight");
         }
         double baseArea = sideLength * sideLength;
         double lateralSurfaceArea = 2 * sideLength * slantHeight;
@@ -232,4 +232,4 @@ public static double surfaceAreaCone(final double radius, final double height) {
         }
         return Math.PI * radius * (radius + Math.pow(height * height + radius * radius, 0.5));
     }
-}
+}