Rewrite listener volume docs

[nightkr]

Description

Fixes #496 (hopefully).

Also moves the listener volume scope to the top of the list and adds caveats to the other scopes.

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1. Code contains useful comments
2. Code contains useful logging statements
3. (Integration-)Test cases added
4. Documentation added or updated. Follows the style guide.
5. Changelog updated
6. Cargo.toml only contains references to git tags (not specific commits or branches)

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1. Feature Tracker has been updated
2. Proper release label has been added
3. Roadmap has been updated

[nightkr]

Particularly curious to hear @razvan's thoughts, though I think it's still a bit more abstract than would be ideal...

[razvan]

thanks!