An example of constructor call with braces - empty braces to fix the most vexing parse problem

Fix #31 (closed)

2-ObjectProgramming/3-constructors-destructor.ipynb

 I advise you to read this very interesting [FluentCpp post](https://www.fluentcpp.com/2018/09/28/auto-stick-changing-style/) about this syntax which ponders about the relunctance we might have to embrace evolution of our languages - so the reading is of interest even for developers using other languages.
 %% Cell type:markdown id: tags:
+### "braces" (`{}`) for constructor calls
+
+Another alternate syntax that removes the ambiguity is the use of braces (`{}`):
+%% Cell type:code id: tags:
+``` C++17
+#include <iostream>
+
+{
+    Vector v1{}; // Constructor Vector()
+    std::cout << v1.norm() << std::endl;
+
+    Vector v2{5., 6., -4.2}; // The other constructor Vector(double x, double y, double z)
+    std::cout << v2.norm() << std::endl;
+}
+%% Cell type:markdown id: tags: