[config.rs] Change path to /etc

[begin-theadventure]

#13

[mqudsi]

Thanks for the PR, @begin-theadventure but this is conflating PREFIX (which isn't something that's just used in this code but actually has some conventions in how it's used by build systems and package managers) with the paths to the configuration files that syngestures searches for. I left some notes in the issue you opened that are relevant to correctly fixing this.

I'm closing this PR out because it changes more than just the config file search logic, but will follow it up with a patch to make sure /etc/syngestures[.toml|.d] is correctly searched, as you are correct in filing a bug for that.