Create hosted demo of a few trained models to put on web site

[neubig]

Some people might be interested in playing around with models that have been trained with prompt2model. Currently, prompt2model supports building gradio demos using the trained models. Here is an example from the CLI demo:

https://github.com/neulab/prompt2model/blob/6515ea87b718def79a2399ef35f1cac67982640c/cli_demo.py#L430

It would be nice to create demos for some tasks that we could host online so people could play around with the models and see how quickly they run and how well they work.