(DOCSP-21748) Add banners to v3 and earlier (#101)

* (DOCSP-21748) Add v3 banners

Author: zach-carr

snooty.toml

@@ -15,3 +15,13 @@ scala-version-full = "2.12.13"
 [substitutions]
 copy = "unicode:: U+000A9"
 ent-build = "MongoDB Enterprise"
+
+[[banners]]
+targets = ["*"]
+variant = "info"
+value = """\
+    MongoDB Connector for Spark comes in two standalone series: version \
+    3.x and earlier, and version 10.x and later. \
+    Use the latest 10.x series of the Connector to take advantage of \
+    native integration with Spark features like Structured Streaming.
+    """