Update docker-compose-nginx.yaml

[EdvardGB]

working nginx example. docker-compose-nginx was missing some configuration to run out of the box.

Description

Oauth2-proxy was missing image, config command and did not spin up dex as the file said it should. Added therefore dex, httpbin and etcd containers.

Motivation and Context

The niginx local example did not work out of the box because of missing docker config.

How Has This Been Tested?

Ran it locally and it worked.

Checklist:

• My change requires a change to the documentation or CHANGELOG.
• I have updated the documentation/CHANGELOG accordingly.
• I have created a feature (non-master) branch for my PR.
• I have written tests for my code changes.