Improve macOS config base directory defaults

[adrg]

Changed defaults for:

XDG_CONFIG_HOME: ~/Library/Preferences to ~/Library/Application Support.
XDG_CONFIG_DIRS: /Library/Preferences to ~/Library/Preferences:/Library/Application Support:/Library/Preferences.

~/Library/Preferences was not a suitable place for application configuration files, as stated in the Apple Developer docs:

This directory contains app-specific preference files. You should not create files in this directory 
yourself. Instead, use the NSUserDefaults class or CFPreferences API to get and set preference
values for your app.

~/Library/Application Support seems like a more appropriate location:

Use this directory to store all app data files except those associated with the user’s documents.
For example, you might use this directory to store app-created data files, configuration files, templates,
or other fixed or modifiable resources that are managed by the app. An app might use this directory to 
store a modifiable  copy of resources contained initially in the app’s bundle. A game might use this 
directory to store new levels purchased by the user and downloaded from a server.

All content in this directory should be placed in a custom subdirectory whose name is that of your app’s
bundle identifier or your company.

Reference.

[codecov]

Codecov Report

Merging #13 (b5336d9) into master (28f7229) will increase coverage by 0.24%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #13      +/-   ##
==========================================
+ Coverage   92.39%   92.63%   +0.24%     
==========================================
  Files           6        6              
  Lines         184      190       +6     
==========================================
+ Hits          170      176       +6     
  Misses         13       13              
  Partials        1        1              

Impacted Files	Coverage Δ
paths_darwin.go	100.00% <100.00%> (ø)

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