Add banner to documentation referencing link to latest version

[tim-finnigan]

Describe the feature

Search engines will link outdated and inconsistent versions of boto3 docs. For example:

Use Case

Example: #4364.

Proposed Solution

Add a banner at the top linking to the latest. For example: pages that reference a specific past version like https://boto3.amazonaws.com/v1/documentation/api/1.35.6/reference/services/s3/client/delete_objects.html, could have a banner/message referring to https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/s3/client/delete_objects.html.

Proposed wording for the banner:

Note: This documentation is for a past release of Boto3. To access the latest version of this documentation, please refer to this page. To update your version of Boto3 please follow the instructions here.