Clean up and document project files (#4560)

docs/mkdocs/docs/examples/items.cpp

@@ -0,0 +1,23 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create JSON values
+    json j_object = {{"one", 1}, {"two", 2}};
+    json j_array = {1, 2, 4, 8, 16};
+
+    // example for an object
+    for (auto& x : j_object.items())
+    {
+        std::cout << "key: " << x.key() << ", value: " << x.value() << '\n';
+    }
+
+    // example for an array
+    for (auto& x : j_array.items())
+    {
+        std::cout << "key: " << x.key() << ", value: " << x.value() << '\n';
+    }
+}