Add banner

Author: 0xTim

Package.resolved

@@ -6,6 +6,10 @@ let languages: [Language] = [
         isDefault: true,
         customStrings: [
             "siteId": "apiDocs",
+            // Announcement banner (shared partials/announce.leaf). announceMessage
+            // shows the banner; clear it to hide. No pill / link for this notice.
+            "announceId": "vapor-week-2026",
+            "announceMessage": "Vapor Week is coming 14th September!",
             "head.defaultOgType": "article",
             "head.homeSuffix": "",
             "head.titleSeparator": " · ",