feat(useInfiniteScroll): new options

[innocenzi]

Description

This PR adds two new options to useInfiniteScroll:

• direction, to chose in which direction to use the infinite scroll
• keepScrollPosition, to automatically compute the scroll position so it stays in place

The current behavior stays the same without explicitly defining these options.

Use case

I was building a chat with infinite scroll, which I want to behave kind of like Discord when you scroll up. For this, I had to revert the direction to top instead of the default bottom, and I needed to keep the scroll position the same after updating the message list.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[vincentbernat]

Did you consider adding direction: both as an option?

[innocenzi]

No I didn't, how would that work and what's the use case?

[vincentbernat]

You could want to browse database records indexed by time of the day in both directions. You start at a given date and you can either scroll up or down. The callback function would need to receive the direction. I may implement that myself once I need it. I was just curious if you already considered it and didn't do it due to some difficulty.

[innocenzi]

Ah true. I just thought of how Discord loads messages too, that's a use case. I didn't consider it because I didn't think of a use case, so I don't know if there are specific difficulties, but I don't think so. Feel free to PR when you need the feature. :)