📝 add more API documentation

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

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+# basic_json::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.
+
+## 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`.
+
+## Exception safety
+
+Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
+
+## Complexity
+
+Linear in the size of the input.
+
+## Example
+
+??? 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.