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/gauge.cpp

@@ -19,7 +19,6 @@ static wchar_t charset[] = L"  ▏▎▍▌▋▊▉█";
 class Gauge : public Node {
  public:
   Gauge(float progress) : progress_(progress) {}
-  ~Gauge() override {}
 
   void ComputeRequirement() override {
     requirement_.flex_grow_x = 1;