Update docs

[NielsRogge]

This PR adds some updates to the docs:

• linking a model or dataset to a paper page (doesn't have to be an Arxiv link)
• submitting a paper in case an author doesn't have one on the hub yet, in order to prevent messages like Release MINT-E dataset on Hugging Face junhua/chain-of-intent#1 (comment)

[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.

[julien-c]

lgtm