Issue #12949: Document the kwonlyargcount argument for the PyCode_New C API function.

Doc/c-api/code.rst

@@ -35,7 +35,7 @@ bound into a function.
 
    Return the number of free variables in *co*.
 
-.. c:function:: PyCodeObject *PyCode_New(int argcount, int nlocals, int stacksize, int flags, PyObject *code, PyObject *consts, PyObject *names, PyObject *varnames, PyObject *freevars, PyObject *cellvars, PyObject *filename, PyObject *name, int firstlineno, PyObject *lnotab)
+.. c:function:: PyCodeObject *PyCode_New(int argcount, int kwonlyargcount, int nlocals, int stacksize, int flags, PyObject *code, PyObject *consts, PyObject *names, PyObject *varnames, PyObject *freevars, PyObject *cellvars, PyObject *filename, PyObject *name, int firstlineno, PyObject *lnotab)
 
    Return a new code object.  If you need a dummy code object to
    create a frame, use :c:func:`PyCode_NewEmpty` instead.  Calling

Misc/NEWS

@@ -418,6 +418,9 @@ Extension Modules
 Documentation
 -------------
 
+- Issue #12949: Document the kwonlyargcount argument for the PyCode_New
+  C API function.
+
 - Issue #2134: The tokenize documentation has been clarified to explain why
   all operator and delimiter tokens are treated as token.OP tokens.