Add proper Falcon docs and conversion script (#25954)

* Add proper Falcon docs and conversion script

* Autodetect the decoder architecture instead of using an arg

* Update docs now that we can autodetect

* Fix doc error

* Add doc to toctree

* Quick doc update

docs/source/en/_toctree.yml

@@ -313,6 +313,8 @@
         title: ErnieM
       - local: model_doc/esm
         title: ESM
+      - local: model_doc/falcon
+        title: Falcon
       - local: model_doc/flan-t5
         title: FLAN-T5
       - local: model_doc/flan-ul2

docs/source/en/model_doc/falcon.md

@@ -0,0 +1,84 @@
+<!--Copyright 2023 The HuggingFace Team. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+the License. You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+specific language governing permissions and limitations under the License.
+
+⚠️ Note that this file is in Markdown but contain specific syntax for our doc-builder (similar to MDX) that may not be
+rendered properly in your Markdown viewer.
+
+-->
+
+# Falcon
+
+## Overview
+
+Falcon is a class of causal decoder-only models built by [TII](https://www.tii.ae/). The largest Falcon checkpoints
+have been trained on >=1T tokens of text, with a particular emphasis on the [RefinedWeb](https://arxiv.org/abs/2306.01116)
+corpus. They are made available under the Apache 2.0 license.
+
+
+Falcon's architecture is modern and optimized for inference, with multi-query attention and support for efficient
+attention variants like `FlashAttention`. Both 'base' models trained only as causal language models as well as
+'instruct' models that have received further fine-tuning are available.
+
+
+Falcon models are (as of 2023) some of the largest and most powerful open-source language models,
+and consistently rank highly in the [OpenLLM leaderboard](https://huggingface.co/spaces/HuggingFaceH4/open_llm_leaderboard).
+
+## Converting custom checkpoints 
+
+<Tip>
+
+Falcon models were initially added to the Hugging Face Hub as custom code checkpoints. However, Falcon is now fully
+supported in the Transformers library. If you fine-tuned a model from a custom code checkpoint, we recommend converting
+your checkpoint to the new in-library format, as this should give significant improvements to stability and
+performance, especially for generation, as well as removing the need to use `trust_remote_code=True`!
+
+</Tip>
+
+You can convert custom code checkpoints to full Transformers checkpoints using the `convert_custom_code_checkpoint.py` 
+script located in the
+[Falcon model directory](https://github.com/huggingface/transformers/tree/main/src/transformers/models/falcon)
+of the Transformers library. To use this script, simply call it with 
+`python convert_custom_code_checkpoint.py --checkpoint_dir my_model`. This will convert your checkpoint in-place, and
+you can immediately load it from the directory afterwards with e.g. `from_pretrained()`. If your model hasn't been
+uploaded to the Hub, we recommend making a backup before attempting the conversion, just in case!
+
+
+## FalconConfig
+
+[[autodoc]] FalconConfig
+    - all
+
+## FalconModel
+
+[[autodoc]] FalconModel
+    - forward
+
+## FalconForCausalLM
+
+[[autodoc]] FalconForCausalLM
+    - forward
+
+## FalconForSequenceClassification
+
+[[autodoc]] FalconForSequenceClassification
+    - forward
+
+## FalconForTokenClassification
+
+[[autodoc]] FalconForTokenClassification
+    - forward
+
+## FalconForQuestionAnswering
+
+[[autodoc]] FalconForQuestionAnswering
+    - forward
+
+