[WIP] Enhance the navigation of comments feature

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

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This section details on the original issue you should resolve

<issue_title>Enhance the navigation of comments</issue_title>
<issue_description>Hi,

As a teacher using Etherpad with my pupils, I get frustrated a lot by the comments feature.
Here is the typical scenario:

1. My students write some text in a pad, making lots of mistakes on one line, lots of mistakes on the line above it and lots of mistakes on the line under it.
2. I give them some feedback on their production using comments such as "Tense", "Typo", etc.
3. They correct and enhance their production according to my comments.
4. I look at the text again and at my comments. If the problem has been addressed, I want to delete the comment; if the problem is the same, I want to tell my students it is so by editing or answering my previous comment.

There comes the trouble. Suppose I have this production with comments on the bold words:

"He sleeps in the house and went out to the garden so he heard some noise there."

Suppose I want to edit the comment on "went", I have to hover over it, and then glide my mouse to the right in a very short amount of time without hovering over "so" or "heard" to avoid triggering their comments... Add up one line above with comments and the same under... Multiply by 100 lines, multiply by 35 pads (one for each pupil) and you get why it becomes frustrating after a while.

I think the problem could be solved if there was a way to navigate from one comment to the next or previous one, such as arrows at the top of a comment.

I hope it is not an issue that's been closed already, I went through the opened ones but forgot to check the closed ones before writing all that text...

Nevertheless, thanks for your work, Etherpad is a great tool for working with pupils!

All best,
Benjamin</issue_description>

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