eliminate warning message in CircleCI logs

[simonsdave]

The following message appears in CircleCI logs.

WARNING! Your password will be stored unencrypted in /root/.docker/config.json.
Configure a credential helper to remove this warning. See
https://docs.docker.com/engine/reference/commandline/login/#credentials-store

Some references that might be useful

• 8 Jun '20 - Encrypted Credentials for Docker Login
• 15 Sep '20 - Docker pass Credential Helper on Ubuntu
• pass = the standard unix password manager
• Docker login command
• Docker Credentials Store