Added content/settings to .npmignore

- this folder should be clean of non-README files in the published package
  so we need to add it to `.npmignore` to ignore any other files

.npmignore

@@ -26,6 +26,8 @@ content/images/**
 !content/images/README.md
 content/logs/**
 !content/logs/README.md
+content/settings/**
+!content/settings/README.md
 content/themes/**
 !content/themes/casper/**
 content/themes/casper/assets/css/.csscomb.json