Bug fixes section release post

Why is this change being made?

Allows a bug fixes section to be added to the release post.

Method

Add a secondary item with the following format:

    - name: "Bug Fixes"
      available_in: [core, starter, premium, ultimate]
      bug_fixes_url: https://gitlab.com/groups/gitlab-org/-/issues?scope=all&utf8=%E2%9C%93&state=merged&label_name%5B%5D=bug&milestone_title=12.7
      reporter: multiple
      description: |
        Some of the notable bug fixes in GitLab 12.6 are:

        - [Zoom quick action on a new issue causes error](https://gitlab.com/gitlab-org/gitlab/issues/38234)
        - [Merge request search: "release tag" filter not working](https://gitlab.com/gitlab-org/gitlab/issues/38244)

• Change Bug Fixes URL to appropriate one for milestone
• Change individual list items

Screenshot

• https://gcs-bug-fixes-section-release-post.about.gitlab-review.app/blog/2019/12/22/gitlab-12-6-released/index.html#bug-fixes (whilst available)

References

Aims to resolve: #5770 (closed)