Add info where config/data will be stored

README

 *plugins*
   folder where plugins are stored
 
+*/etc/gmon/config*
+  system-wide configuration file
+
+*~/.config/gmon/config*
+  user's personal config
+
+*~/.local/share/gmon/plugins/<plugin_name>*
+  plugin local storage (if needed)
+
 
 ENVIRONMENT
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