Remove explicit default destructors (#157)

From CppCoreGuidelines:

Rule of Zero: C.20: If you can avoid defining default operations, do.
C.52: Use inheriting constructors to import constructors into a derived class that does not need further explicit initialization.
DRY forward and using declarations.
Miscellaneous:

Fix format.sh to output examples with normalised paths in sorted order.

Co-authored-by: ArthurSonzogni <sonzogniarthur@gmail.com>

src/ftxui/dom/reflect.cpp

@@ -14,7 +14,6 @@ class Reflect : public Node {
  public:
   Reflect(Element child, Box& box)
       : Node(unpack(std::move(child))), reflected_box_(box) {}
-  ~Reflect() override {}
 
   void ComputeRequirement() final {
     Node::ComputeRequirement();