GPTNeoXForQuestionAnswering (#23059)

* first draft - gives index error in question_answering.py

* maturing

* no labels

* pipeline should know about QA

* fixing checks

* formatting

* fixed docstring

* initial commit

* formatting

* adding the class to many places

* towards less unhappy checks

* nearly there

* and gpt neox for qa

* use right model

* forgot this one

* base_model_prefix is "gpt_neox" for GPTNeoX* models

* unnecessary stuff

* Update src/transformers/models/gpt_neox/modeling_gpt_neox.py

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* format

* Update src/transformers/models/gpt_neox/modeling_gpt_neox.py

Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>

* removed gpt2 stuff

---------

Co-authored-by: Prof. Peter Schneider-Kamp <jps@ordbogen.com>
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>
Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>

docs/source/en/model_doc/gpt_neox.mdx

@@ -79,6 +79,11 @@ The `generate()` method can be used to generate text using GPT Neo model.
 [[autodoc]] GPTNeoXForCausalLM
     - forward
 
+## GPTNeoXForQuestionAnswering
+
+[[autodoc]] GPTNeoXForQuestionAnswering
+    - forward
+
 ## GPTNeoXForSequenceClassification
 
 [[autodoc]] GPTNeoXForSequenceClassification