Add some more IDE configurations in the user manual

[woshilapin]

In the User manual manual.adoc, there is a section to help everyone to set up their favorite IDE/editor. This is great.

I could probably provide a PR for at least two more text editors (Kakoune and Helix).

But first, I wanted to know if this kind of changes would be welcomed. I could understand the desire to keep the list short and only about mainstream IDE/editors. Tell me if you'd like me to contribute or else, you can just close the issue.

[flodiebold]

We have a section for juCi++, which I have never even heard of. So I think it'd be fine to add Kakoune and Helix.