Adds banner to all pages (#119)

* Adds banner to all pages

* Per Ian's review, limits to 3 pages

* Small language tweak

Author: sarahsimpers

snooty.toml

@@ -371,4 +371,11 @@ yaml = ":abbr:`YAML (Yet Another Markup Language)`"
 vercel = "`Vercel <https://www.vercel.com/>`__"
 vercel-mdb = "`MongoDB Atlas Integration in Vercel <https://www.vercel.com/integrations/mongodbatlas>`__"
 vercel-dynamic = "`dynamic IP addresses <https://www.vercel.com/support/articles/how-to-allowlist-deployment-ip-address>`__"
-workload = "Workload Identity Federation"
+workload = "Workload Identity Federation"
+
+[[banners]]
+targets = ["index.txt", "high-availability.txt", "resiliency.txt"]
+variant = "info"
+value = """\
+    The {+atlas-arch-center+} is in early release and includes recommendations for a single-cloud, single-region architecture. MongoDB plans to add multi-region recommendations, recommendations for compliance with external standards, and a plug-and-play Terraform code repository in future releases.
+    """