[EtorixDev]

Adds a plugin to improve backreading a channel.

Currently if you scroll any faster than a snail's pace you're often hit with rubberbanding as Discord pushes your scroll position back down as it renders messages and fetches more.

4 main fixes for that:

1. Prevent the forced scroll adjustment.
2. Start rendering messages sooner/farther "off screen" outside the viewport.
3. Start fetching the next batch of messages sooner/farther "off screen" outside the viewport.
4. Optionally fetch more messages at a time, up to the endpoint limit, so there are less opportunities for loading zones.

Used Codex (6.1 Sol/6 Astra) via T3 Code to investigate the rubberbanding issue, to implement patches and then review logged scroll height and request timings while I scrolled a channel's history, and then to implement the plugin. Manually tested and reviewed each patch/setting individually. PR written and opened manually. Code comments kept intentionally, and reviewed. I like my patches explained in layman's terms.

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