Help user create custom model for Transformers backend remote code models (#16719)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

docs/source/models/supported_models.md

@@ -55,6 +55,10 @@ If your model is neither supported natively by vLLM or Transformers, you can sti
 Simply set `trust_remote_code=True` and vLLM will run any model on the Model Hub that is compatible with Transformers.
 Provided that the model writer implements their model in a compatible way, this means that you can run new models before they are officially supported in Transformers or vLLM!
 
+:::{tip}
+If you have not yet created your custom model, you can follow this guide on [customising models in Transformers](https://huggingface.co/docs/transformers/en/custom_models).
+:::
+
 ```python
 from vllm import LLM
 llm = LLM(model=..., task="generate", trust_remote_code=True)  # Name or path of your model