docs: mention @private

pdoc/__init__.py

@@ -180,13 +180,14 @@ class GoldenRetriever(Dog):
 - If `__all__` is defined in the module, then all identifiers in that list will be considered public.
    No other identifiers will be considered public.
 - If `__all__` is not defined, then pdoc will consider all members public that
-   1. do not start with an underscore
+   1. do not start with an underscore,
+   2. don't have `@private` in their docstring,
    2. and are defined in the current module (i.e. they are not imported).
 
 In general, we recommend keeping these conventions:
 
 - If you want to document a private member, consider making it public.
-- If you want to hide a public member, consider making it private.
+- If you want to hide a public member, consider making it private or add `@private` to their docstring,
 - If you want to document a special `__dunder__` method, the recommended way to do so is
   to not document the dunder method specifically, but to add some usage examples in the class documentation.