[doc] custom_models: mention security features of the Hub (#15768)
[doc] custom_models: mention security features of the Hub (#15768)

* custom_models: tiny doc addition

* mention security feature earlier in the section

Co-authored-by: Steven Liu <1ebe0ee8175e468397de6320df32a9a2952b2711@users.noreply.github.com>
huggingface/transformers,huggingface/transformers,huggingface/transformers,huggingface/transformers