Add a quick description of each CSS folder

themes/wporg-5ftf/css/README.md

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+# CSS Structure
+
+This loosely follows [ITCSS.](https://www.xfive.co/blog/itcss-scalable-maintainable-css-architecture/)
+
+## 01 Settings
+
+Typography, colors, any spacing variables, etc should be set here.
+
+## 02 Tools
+
+This contains any mixins. We inherit the following libraries:
+
+- breakpoint
+- kube
+- modular-scale
+
+## 03 Generic
+
+Any generic styles. Used for normalize & reset styles. We inherit:
+
+- kube
+- normalize
+
+## 04 Base (aka Elements)
+
+Styles for plain html elements. We inherit the base theme's styling here.
+
+## 05 Objects
+
+These are pieces of UI. These should be self-contained (or nested so that they are self-contained). Blocks should
+be defined here.
+
+## 06 Components
+
+This section puts together the base and objects to create pages. Page-specific styles are defined here.
+
+## 07 Utilities
+
+The `is-*`/`has-*` classes, these custom classes override previous styles. For example, `has-background` would be
+defined here.