Update demo-site dependencies and installation instructions

[sroussey]

Upgrade the demo-site to use the latest version of Vite and replace the transformer library with Hugging Face's version, updating installation instructions accordingly. Uses streamer instead of bare callback.

[sroussey]

The text generation example still does not work since it is creating a url where the file name starts with model, but in the case of Xenova/distilgpt2 the file starts with decoder_model

See https://huggingface.co/Xenova/distilgpt2/tree/main/onnx

[sroussey]

If your pipeline tests were not ignored, I think you would have noticed that the summarize test would fail.

[pselvana]

@xenova - Any chance this can be prioritized? The existing @xenova/transformers packages are deprecated and anyone using the demo-site as a starter will find themselves unsupported for newer models.