[Documentation] Outdated pages

### Describe the documentation issue

Listing the outdated docs page here:

- https://onnxruntime.ai/docs/performance/model-optimizations/ort-format-models.html#backwards-compatibility
- https://onnxruntime.ai/docs/reference/operators/
- https://onnxruntime.ai/docs/tutorials/accelerate-pytorch/pytorch.html
- https://onnxruntime.ai/docs/get-started/with-python.html
- Rust: https://onnxruntime.ai/docs/get-started/community-projects.html ORT has an api
- https://onnxruntime.ai/docs/get-started/with-windows.html Mentioning of DirectML
- https://onnxruntime.ai/docs/get-started/training-pytorch.html Mentioning of training
- https://onnxruntime.ai/docs/install/ Missing WebGPU

It would be good to display a "last updated" time stamp on the pages.

Also - we should probably create a new repo for the site https://github.com/microsoft/onnxruntime/tree/gh-pages so that it is not hidden in a branch.

cc @MaanavD