Add CvT (#17299)

* Adding cvt files

* Adding cvt files

* changes in init file

* Adding cvt files

* changes in init file

* Style fixes

* Address comments from code review

* Apply suggestions from code review
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* Format lists in docstring

* Fix copies

* Apply suggestion from code review
Co-authored-by: AnugunjNaman <anugunjjha@gmail.com>
Co-authored-by: Ayushman Singh <singhayushman13@protonmail.com>
Co-authored-by: Niels Rogge <nielsrogge@Nielss-MacBook-Pro.local>
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

utils/documentation_tests.txt

@@ -21,6 +21,7 @@ src/transformers/models/blenderbot/modeling_blenderbot.py
 src/transformers/models/blenderbot_small/modeling_blenderbot_small.py
 src/transformers/models/convnext/modeling_convnext.py
 src/transformers/models/ctrl/modeling_ctrl.py
+src/transformers/models/cvt/modeling_cvt.py
 src/transformers/models/data2vec/modeling_data2vec_audio.py
 src/transformers/models/data2vec/modeling_data2vec_vision.py
 src/transformers/models/deit/modeling_deit.py