update blog handbook
What?
Blog Handbook updates - https://about.gitlab.com/handbook/marketing/blog/
- Discussion: https://docs.google.com/presentation/d/1J9icexWql6q2VgU4Syn0_WsnND5R9l1hYS44Xr9sv_c/edit#slide=id.p
### Tasks
Tasks transferred to https://gitlab.com/gitlab-com/marketing/issues/359
Is part of https://gitlab.com/gitlab-com/marketing/issues/339
cc/ @amara @AshleyS