Ship an official Docker image

[yuvipanda]

• I've read and understood the Contributing guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've searched for any related issues and avoided creating a duplicate issue.

Description

Ship an official Docker image for go-auditd. Should be as simple as adding a Dockerfile here and setting up automated builds on DockerHub. Would be quite useful for folks wanting to run this inside docker containers.

[nbrownus]

The state of auditd and linux containers is a bit weird. You'd need to decide to run go-audit either in each container you have or on the host itself. A dedicated container running go-audit won't provide much value since it would only be monitoring its own container.