WIP: Add reverse proxy example

[awsjdgls]

This is a version of howto-alb that assumes one of the backends runs HTTPS.

HTTPS is not a supported listener protocol (see Listener configuration in the Virtual nodes section of the user guide), but we can work around this by using a reverse proxy to hide it behind an HTTP endpoint exposed via an additional container within the same task.

TODO:

• [ ] Drop the unneeded v1 backend, load balancer, etc.
• [ ] Drop the v1 backend from the readme
• [ ] Document how the reverse proxy works in the readme

Issue #, if available:

Description of changes:

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