[PoC] Add resources to each model's doc page
# What does this PR do?

This PR is a small PoC to add resources (notebooks, scripts, blogs, etc.) to each model's doc page.

Ideally (not sure if it's possible), but it'd be great if we could (partially) automate this.

The idea being that, if a new model is added to the FOR_IMAGE_CLASSIFICATION_MAPPING for instance, the doc page automatically will add a link to the image classification notebooks and scripts. Not sure if this is possible, cc @sgugger.
_The documentation is not available anymore as the PR was closed or merged._<|||||>One question I have: does it matter if the resources diverge from the API described in the docs?<|||||>@stevhliu, I think this is a pretty significant improvement for the model pages. Would you be down to try doing something similar for other high-profile architectures? 

If so, I would encourage the following:
- Identifty the 20 most popular model architectures, either through number of downloads or through doc pages views
- Open an issue to track the update of these 20 most popular architectures.
- Start working on some of them one at a time
- Open this up to community contributions

Would you be down to kickstart such a project? In doing so, I'm sure we'll have more visibility over what we can automate, and what we cannot automate. I'm pretty sure we can automate a portion of it but I don't think we can have high-quality resources here only using automation.<|||||>Closing this PR as it was just a PoC. Will continue the work in other PRs