Revert "fix: Remove pointless Maintenance and Announcement apps (#35852)"

This reverts commit 9274852f2d.

lms/static/sass/_build-lms-v1.scss

@@ -67,6 +67,7 @@
 
 // features
 @import 'features/bookmarks-v1';
+@import "features/announcements";
 @import 'features/_unsupported-browser-alert';
 @import 'features/content-type-gating';
 @import 'features/course-duration-limits';

lms/static/sass/features/_announcements.scss

@@ -0,0 +1,28 @@
+// lms - features - announcements
+// ====================
+.announcements-list {
+  display: inline-block;
+  width: 100%;
+
+  .announcement {
+    background-color: $course-profile-bg;
+    align-content: center;
+    text-align: center;
+    padding: 22px 33px;
+    margin-bottom: 15px;
+  }
+
+  .announcement-button {
+    display: inline-block;
+    padding: 3px 10px;
+    font-size: 0.75rem;
+  }
+
+  .prev {
+    float: left;
+  }
+
+  .next {
+    float: right;
+  }
+}