docs: split bot documentation into separate files with minor fix

[Exirel]

Description

More than the title:

• moved "make it talk", "style", "channels", and "time" in their own file
• talk, style, and channels are in the same sub-folder, time is at the same level as bot and privileges as it made more sense to me
• I fixed a warning that appears in the doc when using the Furo theme about "content table"
• I edited some example, it might be difficult to see them at first, they are in bot/talk.rst (dgw you need to check that, the text is short enough so it shouldn't be too painful)
• I also added a "best practices" section to the "about time" chapter, since we talked about it on IRC and it made sense to add it in a doc-only PR

Checklist

• I have read CONTRIBUTING.md
• I can and do license this contribution under the EFLv2
• No issues are reported by make qa (runs make quality and make test)
• I have tested the functionality of the things this change touches

[dgw]

Just one line note from me this time. I don't think there's much else for me to say yet. Excluding the already-merged "time" page, this PR's net line diff is only about +10, I've explicitly not looked at the moved page contents in any detail because I trust (from skimming) that they're nearly identical.

[Exirel]

I rebased on master so you don't see the other PR's commit in here anymore. I did so after applying your suggestion, which I kept in a separate commit. Nothing else has change since your last review.

[dgw]

Here I am with more thoughts. This is certainly not the end of bikeshedding. 🙀

[Exirel]

@dgw I changed the wording for join/part, and I'm now tempted to write a guideline about time (the thing we discussed on IRC when playing with timeformat) in that PR, if that's cool with you.

[Exirel]

Now with Best Pratices for times:

[dgw]

In other news, I'm thinking (again) about a :pypi: custom Sphinx role…

[Exirel]

Like I said on IRC, I realized that the conflict is more annoying than risky. However, given it's a doc PR, I don't want to rebase & squash before @dgw agree to, otherwise he'll complain about tracking changes. 😁

[dgw]

I saw one more nit, but you can apply it (or not) during the squash. I'm not going to spend the time post-squash checking to make sure you actually used it. 😛

[Exirel]

Applied, squashed & done.