Clean up and document project files (#4560)

docs/mkdocs/docs/examples/operator_literal_json_pointer.cpp

@@ -0,0 +1,14 @@
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+using namespace nlohmann::literals;
+
+int main()
+{
+    json j = R"( {"hello": "world", "answer": 42} )"_json;
+    auto val = j["/hello"_json_pointer];
+
+    std::cout << std::setw(2) << val << '\n';
+}