feat(customIcon): update readme based on feedback

packages/components/icons/README.md

@@ -108,7 +108,9 @@ This component can be used wherever it is necessary to display a themed icon.
 
 ## Custom Icon
 
-The custom icon is a an eye-catching visual element that should be used when an additional visual prominence is needed for displaying a custom SVG icon in the UI.
+This component is meant to be used whenever consumers need to render an icon which is not part of the [ui-kit icon set](https://uikit.commercetools.com/?path=/story/components-icons--all-icons).
+
+In order to keep visual consistency, we want to keep the available sizes of all icons equal. Bear in mind we would expect custom SVG icons to not contain size attributes so it can be controlled based on the components size attribute.
 
 The component is exported as a separate entry point:
 
@@ -132,7 +134,3 @@ const app = () => <Icon icon={<YourCustomIcon />} />;
 | `size`      | `string`                                                  |          | '10', '20', '30', '40'                              | '20'    | Specifies the icon size                         |
 | `icon`      | `union`<br/>Possible values:<br/>`, ReactElement, string` |    -     | A `ReactNode` or `string` that display a custom SVG |         | Icon displayed as a child of this component     |
 | `hasBorder` | `boolean`                                                 |          | `true`, `false`                                     | `false` | Specifies whether the element displays a border |
-
-### Where to use
-
-This component can be used wherever it is necessary to display an icon that is not a UI Kit `<Icon/>` component.