📝 add more API documentation

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

@@ -0,0 +1,52 @@
+# basic_json::array_t
+
+```cpp
+using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;
+```
+
+The type used to store JSON arrays.
+
+[RFC 7159](http://rfc7159.net/rfc7159) describes JSON arrays as follows:
+> An array is an ordered sequence of zero or more values.
+
+To store objects in C++, a type is defined by the template parameters explained below.
+
+## Template parameters
+
+`ArrayType`
+:   container type to store arrays (e.g., `std::vector` or `std::list`)
+
+`AllocatorType`
+:   the allocator to use for objects (e.g., `std::allocator`)
+
+## Notes
+
+#### Default type
+
+With the default values for `ArrayType` (`std::vector`) and `AllocatorType` (`std::allocator`), the default value for
+`array_t` is:
+
+```cpp
+std::vector<
+  basic_json, // value_type
+  std::allocator<basic_json> // allocator_type
+>
+```
+
+#### Limits
+
+[RFC 7159](http://rfc7159.net/rfc7159) specifies:
+> An implementation may set limits on the maximum depth of nesting.
+
+In this class, the array's limit of nesting is not explicitly constrained. However, a maximum depth of nesting may be
+introduced by the compiler or runtime environment. A theoretical limit can be queried by calling the
+[`max_size`](max_size.md) function of a JSON array.
+
+#### Storage
+
+Arrays are stored as pointers in a `basic_json` type. That is, for any access to array values, a pointer of type
+`#!cpp array_t*` must be dereferenced.
+
+## Version history
+
+- Added in version 1.0.0.