Add new blog merchandise for "A Cloud Native Transformation" webcast

Why is this change being made?

This change adds a fifth blog merchandising option for "A Cloud Native Transformation". It links to https://about.gitlab.com/webcast/cloud-native-transformation/.

To include the blog merchandise, just use "merch_five"

This MR also updates the following blog post with the new blog merchandise for testing purposes. /blog/2019/11/04/gitlab-for-gitops-prt-1/

Does this MR meet the acceptance criteria?

Assign to DRI

• Did you assign this change to the correct DRI of the page or information you are changing?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what

Closes #6914