Fix config path information

README.md

 
 **Note:** in this mode `light` runs unpriviliged, so the `/etc/light`
 directory (for cached settings) is not used, instead the per-user
-specific `~/.cache/light` is used.
+specific `~/.config/light` is used.
 
 
 [Light]:     https://github.com/haikarainen/light/