feat: add docker compose example for pact consumer

[Joelasaur]

This is a work in progress, trying to demonstrate the error I'm getting when working with docker compose and pact:

The pact core was unable to write the pact file

So far I'm not able to reproduce it; the docker volume pacts_data is being read just fine by both the example-consumer and pact-cli containers. Not sure how to fix it on my end.

[mefellows]

Thanks. I'm not quite sure how to approach this. Ideally each of our example projects are consistent and repeatable, so I'm not necessarily comfortable about bringing it in here without also bringing it in to all of the others.

Perhaps it's better placed in a separate example project to show the use of docker, or as an example in the Pact JS repo (which is also tested as part of each build).