Reorganize directories (#3462)

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

docs/examples/diff.cpp

@@ -0,0 +1,36 @@
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // the source document
+    json source = R"(
+        {
+            "baz": "qux",
+            "foo": "bar"
+        }
+    )"_json;
+
+    // the target document
+    json target = R"(
+        {
+            "baz": "boo",
+            "hello": [
+                "world"
+            ]
+        }
+    )"_json;
+
+    // create the patch
+    json patch = json::diff(source, target);
+
+    // roundtrip
+    json patched_source = source.patch(patch);
+
+    // output patch and roundtrip result
+    std::cout << std::setw(4) << patch << "\n\n"
+              << std::setw(4) << patched_source << std::endl;
+}