Add Docker template to generate-release-notes script

[a-b]

Starting CLI v8.0.0 we added Docker distribution.

Feature: Docker section in release notes
As cf cli user
I want to see a docker section with prepopulated docker command  in the release notes
So I can easily access docker image with new cf

Resources

• Release notes script: https://github.com/cloudfoundry/cli/blob/19278c3aed08aa3ce867c02467be7e453c5c1c56/bin/generate-release-notes#L22
• Example of the release with a Docker section