MOBILE-3371 core: Implement dimmed empty box

Also improved storybook set up to test the new feature

.storybook/main.js

@@ -1,5 +1,11 @@
 module.exports = {
     framework: '@storybook/angular',
-    addons: ['@storybook/addon-controls'],
+    addons: [
+        '@storybook/addon-controls',
+        '@storybook/addon-viewport',
+        'storybook-addon-designs',
+        'storybook-addon-rtl-direction',
+        'storybook-dark-mode',
+    ],
     stories: ['../src/**/*.stories.ts'],
 }

.storybook/preview.js

@@ -3,4 +3,9 @@ import '!style-loader!css-loader!sass-loader!./styles.scss';
 
 export const parameters = {
     layout: 'centered',
+    darkMode: {
+        darkClass: 'dark',
+        classTarget: 'html',
+        stylePreview: true,
+    },
 };

.storybook/styles.scss

@@ -1,3 +1,7 @@
+storybook-dynamic-app-root {
+    color: var(--ion-text-color);
+}
+
 .core-error-info {
     max-width: 300px;
 }