[ONNX] Document ONNX diagnostics (#88371)
Reference pages:
- Landing page: https://docs-preview.pytorch.org/88371/onnx_diagnostics.html
- Individual rule: https://docs-preview.pytorch.org/88371/generated/onnx_diagnostics_rules/POE0004%3Aoperator-supported-in-newer-opset-version.html
An initial PR to setup the document generation for ONNX diagnostics.
* Add document page for ONNX diagnostics.
* Add document generation for diagnostics rules from `rules.yaml`.
* Add dependency on `myst-parser` for markdown to rst parsing.
More content to be added.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88371
Approved by: https://github.com/abock, https://github.com/justinchuby, https://github.com/malfet, https://github.com/kit1980
