Cleanup package imports in styles.scss

- Remove duplicate entry
- Add missing summary box
- Sort alphabetically
- Add icon and icon list
- Add site alert
- Add collection

src/stylesheets/theme/styles.scss

@@ -36,16 +36,18 @@
 // @import 'packages/validation';
 // @import 'packages/usa-accordion';
 // @import 'packages/usa-alert';
-// @import 'packages/usa-identifier';
 // @import 'packages/usa-banner';
 // @import 'packages/usa-breadcrumb';
-// @import 'packages/usa-button';
 // @import 'packages/usa-button-group';
+// @import 'packages/usa-button';
 // @import 'packages/usa-card';
 // @import 'packages/usa-checklist';
+// @import 'packages/usa-collection';
 // @import 'packages/usa-footer';
 // @import 'packages/usa-header';
 // @import 'packages/usa-hero';
+// @import 'packages/usa-icon-list';
+// @import 'packages/usa-icon';
 // @import 'packages/usa-identifier';
 // @import 'packages/usa-layout';
 // @import 'packages/usa-media-block';
@@ -57,8 +59,10 @@
 // @import 'packages/usa-search';
 // @import 'packages/usa-section';
 // @import 'packages/usa-sidenav';
+// @import 'packages/usa-site-alert';
 // @import 'packages/usa-skipnav';
 // @import 'packages/usa-step-indicator';
+// @import 'packages/usa-summary-box';
 // @import 'packages/usa-table';
 // @import 'packages/usa-tag';