* 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
* docs: Fix typo in ONNX parser help: 'tolerence' => 'tolerance'
* docs: Resolve many typos in the English docs
Typos found via 'codespell ./docs/source/en'