Bug 1932205 - Configure IAB Banner positions r=home-newtab-reviewers,reemhamz

Differential Revision: https://phabricator.services.mozilla.com/D231752

browser/components/newtab/lib/ActivityStream.sys.mjs

@@ -436,6 +436,14 @@ export const PREFS_CONFIG = new Map([
       value: false,
     },
   ],
+  [
+    "newtabAdSize.leaderboard.position",
+    {
+      title:
+        "CSV string of positions for leaderboard spocs - should corralate to a row in DS grid",
+      value: "1",
+    },
+  ],
   [
     "newtabAdSize.billboard",
     {
@@ -443,6 +451,14 @@ export const PREFS_CONFIG = new Map([
       value: false,
     },
   ],
+  [
+    "newtabAdSize.billboard.position",
+    {
+      title:
+        "number string of positions for billboard spocs - should corralate to a row in DS grid",
+      value: "1",
+    },
+  ],
   [
     "newtabLayouts.variant-a",
     {