Add containerPort option to avoid using HTTPS port 443 for plain HTTP

[denis-ryzhkov]

I was confused by HTTPS port 443 being used also as containerPort with plain HTTP traffic.

Seeing that health checks fail trying to access my docker image via port 443, while it expects port 8080, lead me to adding containerPort option to this plugin copy to clearly have port: 443 for HTTPS ALB listener and containerPort: 8080 for HTTP in TargetGroup and ECS container, to see clear SSL unwrapping happening at ALB.

Later I discovered the true reason of health check failure was the issue #2 I reported, so please fix that issue first.

But to avoid further confusion of other users of this plugin regarding HTTPS port != HTTP containerPort, please also review and merge this PR

[gwdp]

Since we are talking about the port used between the ALB and the container I always had the assumption you could map out the container port to be 443 independently of the protocol, but you are totally right, there are use cases where we could want to route to a different port. Building and bumping npm later tonight.

Really thanks for the contribution, appreciate it :)