feat: Add scrollbar

[peso]

This PR adds scrollbars to windows that can scroll. This gives a visual indicator of how far you have scrolled.

[istudyatuni]

Tested, looks good, thanks! Will review soon™

[istudyatuni]

I refactored scrollbar widget a bit. Also I think single line for scrollbar track is better than double in this case

[istudyatuni]

I rephrased comment a bit and removed todo: minus 1 comments, as I understand, -1 is not needed because we passing count of elements, and Scrollbar widget handle it

[istudyatuni]

@Cretezy could you enable rebase merge? I don't want to loose commit history

[peso]

The TODO note was because I forgot why I did a -1 in the first place, but I rediscovered during testing:
The thumb cannot reach the bottom unless content_length is equal to the largest possible scroll-position. (So "Maximum" would have been a better term ;-) )
I included your comment rephrasing in the last push.

[istudyatuni]

When I tested it, it worked well, reaching the bottom just fine when the cursor was at the last element (didn't test your last change)

[peso]

Apparently the scroll offset bug is a known problem: ratatui/ratatui#1681
Should I remove the -1 for now, file a bug on lazyjj, answer it myself with a reference to the ratatui issue?
I will also make a PR to ratatui, so this is just to get the current PR completed.

[peso]

It seems like the terminal height affects the thumb position.

Example

Example with scroll not reaching bottom

Example where it does

[istudyatuni]

file a bug on lazyjj

I think we can ignore it, since this problem is rare. When this issue will be fixed in ratatui, we will just get fix with an update

---

Also, about splitting to logical commits:

1. Some changes which should be in "refactor: Improve api of DetailsPanel" are in "feat: Scroll bars ..." commits
2. Maybe collapse all "feat: Scroll bars ..." commits into one?

[peso]

I see your point on DetailsPanel api. I guess I'm still learning when is the best time to use "jj absorb". I will move these changes.

Given that this further simplifies the "feat Scroll bar" commits, I can see your point on merging them. I will merge these 4 changes into 1.

[peso]

This should be ready to merge. @Cretezy, are there any more things I need to do?

[istudyatuni]

I can merge too, I just want to do "rebase" merge, not "squash"

[dotdash]

If we don't want to wait, and you want to keep the individual commits (I'd want to, too), the slightly annoying approach would be to create individual PRs for them. 🤷🏻

[peso]

Lets be pragmatic. I'd much prefer the individual commits but if the project prefers squashing PR then so be it. The other approach feels like working around the intention of project management. I will prefer good social relations over individual commits any day.