Reorganize directories (#3462)

* 🚚 move files
* 🚚 rename doc folder to docs
* 🚚 rename test folder to tests

docs/examples/parse__iterator_pair.cpp

@@ -0,0 +1,15 @@
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // a JSON text given an input with other values
+    std::vector<std::uint8_t> input = {'[', '1', ',', '2', ',', '3', ']', 'o', 't', 'h', 'e', 'r'};
+
+    // parse and serialize JSON
+    json j_complete = json::parse(input.begin(), input.begin() + 7);
+    std::cout << std::setw(4) << j_complete << "\n\n";
+}