Update README.md to include ONNX

[alvarobartt]

What does this PR do?

This PR simply includes ONNX among the listed features, as well as mentioning that's the recommended approach when installing from source via cargo install --path router -F ort. Also this PR fixes the casing in CUDA.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline, Pull Request section?
• Was this discussed/approved via a Github issue or the forum? Please add a link to it if that's the case.
• Did you make sure to update the documentation with your changes? Here are the documentation guidelines, and here are tips on formatting docstrings.
• Did you write any new necessary tests?

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