Studies: add a cover image setting, used as the backdrop of the featured study card on the homepage; v2.36.0

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/content.ts

@@ -11,6 +11,8 @@ export interface StudyProgram {
   description: string
   bibleBook?: string
   homepageEyebrow?: string
+  // Cover image for the study, used as the backdrop of the featured card on the homepage
+  imageUrl?: string
   showOnHomepage?: boolean
   showNewTag?: boolean
   newTagLabel?: string