Add cross links for model contribution (#42207)
* add cross links
* a few nits
* last bit
* Update CONTRIBUTING.md
Co-authored-by: Pablo Montalvo <39954772+molbap@users.noreply.github.com>
* Update docs/source/en/transformers_as_backend.md
Co-authored-by: Pablo Montalvo <39954772+molbap@users.noreply.github.com>
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Co-authored-by: Pablo Montalvo <39954772+molbap@users.noreply.github.com>
