bpo-38387: Formally document PyDoc_STRVAR and PyDoc_STR macros (GH-16607)
Adds a short description of `PyDoc_STRVAR` and `PyDoc_STR` to "Useful macros" section of C-API docs.
Currently, there is [one lone mention](https://docs.python.org/3/c-api/module.html?highlight=pydoc_strvar#c.PyModuleDef) in the C-API reference, despite the fact that `PyDoc_STRVAR` is ubiquitous to `Modules/`.
Additionally, this properly uses `c:macro` within `Doc/c-api/module.rst` to link.
diff --git a/Doc/c-api/module.rst b/Doc/c-api/module.rst
index cf1df28..8a415df 100644
--- a/Doc/c-api/module.rst
+++ b/Doc/c-api/module.rst
@@ -153,7 +153,7 @@
.. c:member:: const char *m_doc
Docstring for the module; usually a docstring variable created with
- :c:func:`PyDoc_STRVAR` is used.
+ :c:macro:`PyDoc_STRVAR` is used.
.. c:member:: Py_ssize_t m_size