Clean up and document project files (#4560)

docs/mkdocs/docs/examples/json_pointer__parent_pointer.cpp

@@ -0,0 +1,18 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // different JSON Pointers
+    json::json_pointer ptr1("");
+    json::json_pointer ptr2("/foo");
+    json::json_pointer ptr3("/foo/0");
+
+    // call parent_pointer()
+    std::cout << std::boolalpha
+              << "parent of \"" << ptr1 << "\" is \"" << ptr1.parent_pointer() << "\"\n"
+              << "parent of \"" << ptr2 << "\" is \"" << ptr2.parent_pointer() << "\"\n"
+              << "parent of \"" << ptr3 << "\" is \"" << ptr3.parent_pointer() << "\"" << std::endl;
+}