ANNOUNCEMENT: New maintainers for S3Middleware

[Gregory Neagle]

https://github.com/munki/S3Middleware now has new maintainers that actually use the middleware (while I ported the middleware from Python to Swift, I don’t actually use it)!

Thank you to Adam Anklewicz (@aanklewicz) and Alan Siu (@aysiu) for taking over responsibility for this middleware.

There are still more middleware modules available for adoption:

- https://github.com/munki/AzureStorageMiddleware

- https://github.com/munki/BunnyNetMiddleware

- https://github.com/munki/CloudFrontMiddleware

- https://github.com/munki/GCSMiddleware