feat: new course outline header [FC-0114] (#2735)

Adds new header and subheader to course outline. Converts existing js code to ts.

src/data/api.ts

@@ -67,6 +67,7 @@ export async function getCourseDetails(courseId: string, username: string): Prom
  */
 export const waffleFlagDefaults = {
   enableCourseOptimizer: false,
+  enableNotifications: false,
   enableCourseOptimizerCheckPrevRunLinks: false,
   useNewHomePage: true,
   useNewCustomPages: true,

src/data/types.ts

@@ -123,3 +123,15 @@ export interface XBlock {
   discussionEnabled?: boolean;
   upstreamInfo?: UpstreamInfo;
 }
+
+interface OutlineError {
+  data?: string;
+  type: string;
+}
+
+export interface OutlinePageErrors {
+  outlineIndexApi?: OutlineError | null,
+  reindexApi?: OutlineError | null,
+  sectionLoadingApi?: OutlineError | null,
+  courseLaunchApi?: OutlineError | null,
+}