Update webjobs queue extension CHANGELOG.md for base64 (Azure#18325)

Provided a sample host.json to make it easier for functions uses to take advantage of the ability to opt-out of base64 encoding.

sdk/storage/Microsoft.Azure.WebJobs.Extensions.Storage.Queues/CHANGELOG.md

@@ -3,8 +3,15 @@
 ## 5.0.0-beta.2 (Unreleased)
 
 ### Major changes and features 
-- This version Base64-encodes queue messages by default. This behavior can be changed by setting `QueuesOptions.MessageEncoding`.
-
+- This version Base64-encodes/decodes queue messages by default. This reverses the breaking change in 5.0.0-beta1, and preserves compability with previous major versions. This behavior can be changed by setting `QueuesOptions.MessageEncoding`. For example, to configure Azure Functions to perform no base64 encoding/decoding, specify the following in host.json
+
+```
+  "extensions": {
+    "queues": {
+      "messageEncoding": "none"
+    }
+  }
+```
 
 ## 5.0.0-beta.1 (2020-11-10)