[refs #3] Add content for core settings

Author: Dennis Heibült

_docs/settings/core.md

@@ -10,4 +10,15 @@ filename: "_settings.core.scss"
 
 {% include file-info.html %}
 
-Core settings
+This is probably the most important file of the whole framework. It provides some really far-reaching Sass variables which—when altered—can change the look of your application massivley. That's why you should determine the values of the variables right at the beginning of your project.
+
+The two most important variables are:
+
+    $inuit-global-font-size:    16px !default;
+    $inuit-global-line-height:  24px !default;
+
+The following is very important:
+
+    $inuit-global-spacing-unit: round($inuit-global-line-height) !default;
+
+What this does is reassigning the global line-height to a multipurpose spacing variable