Improve performance of onnx.ai/models

ONNX Model Zoo is now accessed through a webpage onnx.ai/models. This webpage is powered by github pages that reads the directory strucutre from github.com/onnx/models to populate the webpage.
The initial load of the webpage takes > 5sec due to the need to parse 1 yaml file per model to read Author, license and task information.

Proposed Solution:
Add a post merge hook in github.com/onnx/models that generates a json file on every merge that has the following structure per onnx model:

Model Name:
    URL
    Task
    Author Name
    License

This file can be then consumed by github pages instead of parsing 1000's of yaml files at load time.