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/size.cpp

@@ -19,8 +19,6 @@ class Size : public Node {
         constraint_(constraint),
         value_(value) {}
 
-  ~Size() override {}
-
   void ComputeRequirement() override {
     Node::ComputeRequirement();
     requirement_ = children_[0]->requirement();