Update JSON example and add section on special cases

Removed code block formatting for JSON example and added a section header for special cases.

doc/basics.md

@@ -1385,7 +1385,6 @@ struct Car {
   std::vector<float> tire_pressure;
 };
 
-```cpp
 std::string json =  R"( { "make": "Toyota", "model": "Camry",  "year": 2018,
        "tire_pressure": [ 40.1, 39.9 ] } )";
 simdjson::ondemand::parser parser;
@@ -1401,7 +1400,7 @@ maps it to parsing code. We call the default constructor,
 and then assign values to the public members.
 
 
-```
+#### Special cases 
 
 However, there are instances where the construction cannot
 be easily automated. Let us consider a class without any