📝 add more API documentation

doc/mkdocs/docs/api/basic_json/get.md

@@ -10,6 +10,13 @@ ValueType get() const noexcept(
 // (2)
 template<typename BasicJsonType>
 BasicJsonType get() const;
+
+// (3)
+template<typename PointerType>
+PointerType get_ptr();
+
+template<typename PointerType>
+constexpr const PointerType get_ptr() const noexcept;
 ```
 
 1. Explicit type conversion between the JSON value and a compatible value which is
@@ -52,7 +59,9 @@ BasicJsonType get() const;
 2. Overload for `basic_json` specializations. The function is equivalent to executing
     ```cpp
     return *this;
-    ``` 
+    ```
+
+3. Explicit pointer access to the internally stored JSON value. No copies are made.
 
 ## Template parameters
 
@@ -62,15 +71,28 @@ BasicJsonType get() const;
 `BasicJsonType`
 :   a specialization of `basic_json`
 
+`PointerType`
+:   pointer type; must be a pointer to [`array_t`](array_t.md), [`object_t`](object_t.md), [`string_t`](string_t.md),
+    [`boolean_t`](boolean_t.md), [`number_integer_t`](number_integer_t.md), or [`number_unsigned`](number_unsigned.md),
+    [`number_float_t`](number_float_t.md), or [`binary_t`](binary_t.md). Other types will not compile.
+
 ## Return value
 
 1. copy of the JSON value, converted to `ValueType`
 2. a copy of `#!cpp *this`, converted into `BasicJsonType`
+3. pointer to the internally stored JSON value if the requested pointer type fits to the JSON value; `#!cpp nullptr`
+   otherwise
 
 ## Exceptions
 
 Depends on what `json_serializer<ValueType>` `from_json()` method throws
 
+## Notes
+
+!!! warning
+
+    Writing data to the pointee (overload 3) of the result yields an undefined state.
+
 ## Example
 
 ??? example
@@ -91,7 +113,23 @@ Depends on what `json_serializer<ValueType>` `from_json()` method throws
     --8<-- "examples/get__ValueType_const.output"
     ```
 
+??? example
+
+    The example below shows how pointers to internal values of a JSON value can be requested. Note that no type
+    conversions are made and a `#cpp nullptr` is returned if the value and the requested pointer type does not match.
+        
+    ```cpp
+    --8<-- "examples/get__PointerType.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/get__PointerType.output"
+    ```
+
 ## Version history
 
 1. Since version 2.1.0.
 2. Since version 2.1.0. Extended to work with other specializations of `basic_json` in version 3.2.0.
+3. Since version 1.0.0.