Add insertion operator for Grid class

include/aoc/common/Grid.hpp

@@ -15,6 +15,7 @@
 
 #pragma once
 
+#include <iostream>
 #include <memory>
 
 #include <aoc/common/Point2.hpp>
@@ -65,4 +66,20 @@ class Grid
     size_t nRows_;
     size_t nColumns_;
     std::unique_ptr<T[]> data_;
+    friend std::ostream& operator<< <>(std::ostream& os, const Grid<T>& rhs);
 };
+
+template <typename T>
+std::ostream& operator<<(std::ostream& os, const Grid<T>& rhs)
+{
+    size_t i{ 0 };
+    for (size_t j = 0; j < rhs.getNRows(); j++)
+    {
+        for (; i < j * rhs.getNColumns(); i++)
+        {
+            os << rhs.data_[i] << ' ';
+        }
+        os << std::endl;
+    }
+    return os;
+}