Update release scripts / instructions to include Docker

**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
I had to manually edit the vote email to include information about the Docker image.

See https://lists.apache.org/thread/sm3k6mv8fb7ylhmjs96s2zqlnwqvqp12

**Describe the solution you'd like**
Automate this

**Describe alternatives you've considered**
None

**Additional context**