more documentation

In this commit, also the semantics for values skipped via the parser
callback has changed. Now, the top-level value is returned as “null”
instead of “discarded”.

doc/examples/swap__array_t.cpp

@@ -0,0 +1,19 @@
+#include <json.hpp>
+
+using namespace nlohmann;
+
+int main()
+{
+    // create a JSON value
+    json value = {{"array", {1, 2, 3, 4}}};
+
+    // create an array_t
+    json::array_t array = {"Snap", "Crackle", "Pop"};
+
+    // swap the array stored in the JSON value
+    value["array"].swap(array);
+
+    // output the values
+    std::cout << "value = " << value << '\n';
+    std::cout << "array = " << array << '\n';
+}