Reorganize directories (#3462)

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

docs/mkdocs/docs/api/macros/json_has_cpp_11.md

@@ -0,0 +1,28 @@
+# JSON_HAS_CPP_11, JSON_HAS_CPP_14, JSON_HAS_CPP_17, JSON_HAS_CPP_20
+
+```cpp
+#define JSON_HAS_CPP_11
+#define JSON_HAS_CPP_14
+#define JSON_HAS_CPP_17
+#define JSON_HAS_CPP_20
+```
+
+The library targets C++11, but also supports some features introduced in later C++ versions (e.g., `std::string_view`
+support for C++17). For these new features, the library implements some preprocessor checks to determine the C++
+standard. By defining any of these symbols, the internal check is overridden and the provided C++ version is
+unconditionally assumed. This can be helpful for compilers that only implement parts of the standard and would be
+detected incorrectly.
+
+## Default definition
+
+The default value is detected based on preprocessor macros such as `#!cpp __cplusplus`, `#!cpp _HAS_CXX17`, or
+`#!cpp _MSVC_LANG`.
+
+## Notes
+
+- `#!cpp JSON_HAS_CPP_11` is always defined.
+- All macros are undefined outside the library.
+
+## Version history
+
+- Added in version 3.10.5.