Update docs site docs

Review and update all documentation related to the website and tooling.

• Contributor docs: https://new.docs.gitlab.com/development/documentation/ (and all sub-pages) (draft: gitlab-org/gitlab!176057)
• Docs site self-hosting docs. This might not need any updates, but TBD.
• Issue templates: TW onboarding and other team processes (draft: gitlab-org/technical-writing!302)
• Handbook: https://handbook.gitlab.com/handbook/product/ux/technical-writing/ (and all sub-pages)
• Issue template: monthly chores
• Issue template: release process
• Technical docs in this project's doc directory
• Project files: LICENSE (done), CONTRIBUTING.md (done), CODEOWNERS (done), README.md
• README.md in gitlab-docs to note new project location
• Infra service catalog entry: https://gitlab.com/gitlab-com/runbooks/-/blob/master/services/service-catalog.yml?ref_type=heads#L256
• Create a brief reference document to outline all the contributor-facing changes that are coming from this project (e.g, title in front matter, shortcodes, index file naming, creating a release, monthly chores, etc)

We need to prepare these MRs in advance, and get reviews, but anything outside of this project should not merge until Hugo has launched (#44).

Docs MRs to merge post-launch

MR	Status In-progress, Review, Ready
Draft: Update TW project docs for Hugo launch (gitlab-org/technical-writing!302) • Sarah German	In-progress
Draft: Update docs on docs for Hugo launch (gitlab-org/gitlab!176057) • Sarah German • Next 1-3 releases	In-progress