Reorganize directories (#3462)

* 🚚 move files
* 🚚 rename doc folder to docs
* 🚚 rename test folder to tests

docs/mkdocs/docs/api/basic_json/from_msgpack.md

@@ -0,0 +1,109 @@
+# <small>nlohmann::basic_json::</small>from_msgpack
+
+```cpp
+// (1)
+template<typename InputType>
+static basic_json from_msgpack(InputType&& i,
+                               const bool strict = true,
+                               const bool allow_exceptions = true);
+// (2)
+template<typename IteratorType>
+static basic_json from_msgpack(IteratorType first, IteratorType last,
+                               const bool strict = true,
+                               const bool allow_exceptions = true);
+```
+
+Deserializes a given input to a JSON value using the MessagePack serialization format.
+
+1. Reads from a compatible input.
+2. Reads from an iterator range.
+
+The exact mapping and its limitations is described on a [dedicated page](../../features/binary_formats/messagepack.md).
+
+## Template parameters
+
+`InputType`
+:   A compatible input, for instance:
+    
+    - an `std::istream` object
+    - a `FILE` pointer
+    - a C-style array of characters
+    - a pointer to a null-terminated string of single byte characters
+    - an object `obj` for which `begin(obj)` and `end(obj)` produces a valid pair of iterators.
+
+`IteratorType`
+:   a compatible iterator type
+
+## Parameters
+
+`i` (in)
+:   an input in MessagePack format convertible to an input adapter
+
+`first` (in)
+:   iterator to start of the input
+
+`last` (in)
+:   iterator to end of the input
+
+`strict` (in)
+:   whether to expect the input to be consumed until EOF (`#!cpp true` by default)
+
+`allow_exceptions` (in)
+:   whether to throw exceptions in case of a parse error (optional, `#!cpp true` by default)
+
+## Return value
+
+deserialized JSON value; in case of a parse error and `allow_exceptions` set to `#!cpp false`, the return value will be
+`value_t::discarded`.  The latter can be checked with [`is_discarded`](is_discarded.md).
+
+## Exception safety
+
+Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
+
+## Exceptions
+
+- Throws [parse_error.110](../../home/exceptions.md#jsonexceptionparse_error110) if the given input ends prematurely or
+  the end of  file was not reached when `strict` was set to true
+- Throws [parse_error.112](../../home/exceptions.md#jsonexceptionparse_error112) if unsupported features from
+  MessagePack were used in the given input or if the input is not valid MessagePack
+- Throws [parse_error.113](../../home/exceptions.md#jsonexceptionparse_error113) if a string was expected as map key,
+  but not found
+
+## Complexity
+
+Linear in the size of the input.
+
+## Examples
+
+??? example
+
+    The example shows the deserialization of a byte vector in MessagePack format to a JSON value.
+     
+    ```cpp
+    --8<-- "examples/from_msgpack.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/from_msgpack.output"
+    ```
+
+## Version history
+
+- Added in version 2.0.9.
+- Parameter `start_index` since version 2.1.1.
+- Changed to consume input adapters, removed `start_index` parameter, and added `strict` parameter in version 3.0.0.
+- Added `allow_exceptions` parameter in version 3.2.0.
+
+!!! warning "Deprecation"
+
+    - Overload (2) replaces calls to `from_msgpack` with a pointer and a length as first two parameters, which has been
+      deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
+      `#!cpp from_msgpack(ptr, len, ...);` with `#!cpp from_msgpack(ptr, ptr+len, ...);`.
+    - Overload (2) replaces calls to `from_cbor` with a pair of iterators as their first parameter, which has been
+      deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
+      `#!cpp from_msgpack({ptr, ptr+len}, ...);` with `#!cpp from_msgpack(ptr, ptr+len, ...);`.
+
+    You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated
+    function.