New review comment by heittpr on void-packages repository

https://github.com/void-linux/void-packages/pull/33393#discussion_r723801871

Comment:
Didn't think of that lol, but btw, do you think it's worth it to add this to [the manual](https://github.com/void-linux/void-packages/blob/master/Manual.md#writing-runit-services) as well? Since it suggests using `[ -r conf ]`.