Add containers project with CMake setup and array-related functionality

- Implement `printArrayAtPosition` in `functions.cpp` with input validation.
- Created `main.cpp` to demonstrate array operations using C arrays and `std::vector`.
- Updated `ClassA` and `IComparable` with constructors, destructors, and deep copy logic.
- Adjusted IntelliJ project configuration for new containers module.

cpp/classes/ClassA.h

@@ -8,15 +8,23 @@ class ClassA : public IComparable {
 
 public:
     // public
+    ClassA(); // default constructor
+    ClassA(const ClassA& other); // copy constructor
+    ~ClassA() override; // destructor
+
     void Print();
     int CompareTo(IComparable* other) override;
 
+    const float& GetDecimal() const { return *_pDecimal; }
+    void SetDecimal(float decimal) { *_pDecimal = decimal; }
+
 protected:
     // protected
 
 private:
     // private
     int _number = 0;
+    float* _pDecimal = nullptr;
 };