Add Document Image Transformer (DiT) (#15984)

* Add conversion script

* Improve script

* Fix bug

* Add option to push to hub

* Add support for classification models

* Update model name

* Upload feature extractor files first

* Remove hash checking

* Fix config

* Add id2label

* Add import

* Fix id2label file name

* Fix expected shape

* Add model to README

* Improve docs

* Add integration test and fix CI

* Fix code style

* Add missing init

* Add model to SPECIAL_MODULE_TO_TEST_MAP

Co-authored-by: Niels Rogge <nielsrogge@Nielss-MacBook-Pro.local>

docs/source/_toctree.yml

@@ -194,6 +194,8 @@
       title: DialoGPT
     - local: model_doc/distilbert
       title: DistilBERT
+    - local: model_doc/dit
+      title: DiT
     - local: model_doc/dpr
       title: DPR
     - local: model_doc/electra