LibJS: Implement multiplication and division operators

Author: https://github.com/deoxxa
Commit: fdf7f81ba9
Pull-request: https://github.com/SerenityOS/serenity/pull/1425
Reviewed-by: https://github.com/sunverwerth

Libraries/LibJS/Value.cpp

@@ -145,7 +145,6 @@ Value right_shift(Value lhs, Value rhs)
 }
 
 Value add(Value lhs, Value rhs)
-
 {
     ASSERT(lhs.is_number());
     ASSERT(rhs.is_number());
@@ -159,6 +158,20 @@ Value sub(Value lhs, Value rhs)
     return Value(lhs.as_double() - rhs.as_double());
 }
 
+Value mul(Value lhs, Value rhs)
+{
+    ASSERT(lhs.is_number());
+    ASSERT(rhs.is_number());
+    return Value(lhs.as_double() * rhs.as_double());
+}
+
+Value div(Value lhs, Value rhs)
+{
+    ASSERT(lhs.is_number());
+    ASSERT(rhs.is_number());
+    return Value(lhs.as_double() / rhs.as_double());
+}
+
 Value typed_eq(Value lhs, Value rhs)
 {
     if (rhs.type() != lhs.type())