Reorganize directories (#3462)

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

docs/mkdocs/docs/api/macros/json_no_io.md

@@ -0,0 +1,21 @@
+# JSON_NO_IO
+
+```cpp
+#define JSON_NO_IO
+```
+
+When defined, headers `<cstdio>`, `<ios>`, `<iosfwd>`, `<istream>`, and `<ostream>` are not included and parse functions
+relying on these headers are excluded. This is relevant for environments where these I/O functions are disallowed for
+security reasons (e.g., Intel Software Guard Extensions (SGX)).
+
+## Default definition
+
+By default, `#!cpp JSON_NO_IO` is not defined.
+
+```cpp
+#undef JSON_NO_IO
+```
+
+## Version history
+
+- Added in version 3.10.0.