Update docs about Keras models

[Wauplin]

Related to https://github.com/keras-team/keras/pull/19854, https://github.com/huggingface/huggingface.js/pull/774 and https://github.com/huggingface/moon-landing/pull/10501 (private).

This PR updates the doc page about Keras to explain how to load/save models to the Hub using Keras nativly. For now we don't have proper examples yet but it's still better than the current outdated one.

For review, see:

• https://moon-ci-docs.huggingface.co/docs/hub/pr_1320/en/keras
• https://moon-ci-docs.huggingface.co/docs/hub/pr_1320/en/tf-keras

[HuggingFaceDocBuilderDev]

It looks like you've updated documentation related to model or dataset cards in this PR.

Some content is duplicated among the following files. Please make sure that everything stays consistent.

• modelcard.md
• docs/hub/model-cards.md
• docs/hub/model-card-annotated.md
• src/.../modelcard_template.md (huggingface_hub repo)
• src/.../datasetcard_template.md (huggingface_hub repo)
• src/.../repocard.py (huggingface_hub repo)
• datasetcard.md
• docs/hub/datasets-cards.md

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.