GitLab

* first draft of model summary

* restructure docs

* finish first draft

* ✨minor reviews and edits

* apply feedbacks

* save important info, create new page for attention

* add attention doc to toctree

* ✨ few more minor fixes

Update documentation on seq2seq models with absolute positional embeddings, to be in line with Tips section for BERT and GPT2 (#20068)
Co-authored-by: jordiclive <jordiclive19@imperial.ac.uk>

* Reorganize doc for multilingual support

* Fix style

* Style

* Toc trees

* Adapt templates

* Convert all tutorials and guides

* Convert all remaining rst to mdx

* Track and fix bad links