Reorganize directories (#3462)

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

docs/examples/diagnostics_extended.cpp

@@ -0,0 +1,22 @@
+#include <iostream>
+
+# define JSON_DIAGNOSTICS 1
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    json j;
+    j["address"]["street"] = "Fake Street";
+    j["address"]["housenumber"] = "12";
+
+    try
+    {
+        int housenumber = j["address"]["housenumber"];
+    }
+    catch (json::exception& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+}