Updated nlohmann::basicjson::get (markdown)

nlohmann::basicjson::get.md

@@ -24,6 +24,8 @@ The return value is the JSON container's value casted to the return value type `
 | object     | `object_t`, any associative container whose `key_type` convertible from `string_t` and whose `mapped_type ` is convertible from `basic_json` |
 | array      | `array_t`, any sequence container whose `value_type` is convertible from `basic_json`; furthermore, `std::set` and `std::unordered_set` with the same constraints are allowed |
 
+Note that in case of objects and arrays, all values must be compatible.
+
 ## Complexity
 
 Amortized linear in the size of the JSON type.