Reorganize docs contrib guide (#9510)

* Reorganize docs contrib guide

* Address first round of feedback from Brad, Jared

* Standardize on 'SIG Docs'

* Address more feedback

* Rewrites to participating.md

* Tweak navigation titles

* Document PR Wrangler

* Document SIG Docs chairperson

* Fix codeblock that shows how to use <codenew>

It was being interpreted as a Hugo shortcode.

content/en/docs/contribute/_index.md

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+---
+content_template: templates/concept
+title: Contribute to Kubernetes docs
+linktitle: Contribute
+main_menu: true
+weight: 80
+---
+
+{{% capture overview %}}
+
+If you would like to help contribute to the Kubernetes documentation or website,
+we're happy to have your help! Anyone can contribute, whether you're new to the
+project or you've been around a long time, and whether you self-identify as a
+developer, an end user, or someone who just can't stand seeing typos.
+
+Looking for the [style guide](/docs/contribute/style/style-guide/)?
+{{% /capture %}}
+
+{{% capture body %}}
+
+## Types of contributor
+
+- A _member_ of the Kubernetes organization has [signed the CLA](/contribute/start#sign-the-cla)
+  and contributed some time and effort to the project. See
+  [Community membership](https://github.com/kubernetes/community/blob/master/community-membership.md)
+  for specific criteria for membership.
+- A SIG Docs _reviewer_ is a member of the Kubernetes organization who has
+  expressed interest in reviewing documentation pull requests and who has been
+  added to the appropriate Github group and `OWNERS` files in the Github
+  repository, by a SIG Docs Approver.
+- A SIG Docs _approver_ is a member in good standing who has shown a continued
+  commitment to the project and is granted the ability to merge pull requests
+  and thus to publish content on behalf of the Kubernetes organization.
+  Approvers can also represent SIG Docs in the larger Kubernetes community.
+  Some of the duties of a SIG Docs approver, such as coordinating a release,
+  require a significant time commitment.
+
+## Ways to contribute
+
+This list is divided into things anyone can do, things Kubernetes organization
+members can do, and things that require a higher level of access and familiarity
+with SIG Docs processes. Contributing consistently over time can help you
+understand some of the tooling and organizational decisions that have already
+been made.
+
+This is not an exhaustive list of ways you can contribute to the Kubernetes
+documentation, but it should help you get started.
+
+- [Anyone](/docs/contribute/start/)
+  - File actionable bugs
+- [Member](/docs/contribute/start/)
+  - Improve existing docs
+  - Bring up ideas for improvement on Slack or SIG docs mailing list
+  - Improve docs accessibility
+  - Provide non-binding feedback on PRs
+  - Write a blog post or case study
+- [Reviewer](/docs/contribute/intermediate/)
+  - Document new features
+  - Triage and categorize issues
+  - Review PRs
+  - Create diagrams, graphics assets, and embeddable screencasts / videos
+  - Localization
+  - Contribute to other repos as a docs representative
+  - Edit user-facing strings in code
+  - Improve code comments, Godoc
+- [Approver](/docs/contribute/advanced/)
+  - Publish contributor content by approving and merging PRs
+  - Participate in a Kubernetes release team as a docs representative
+  - Propose improvements to the style guide
+  - Propose improvements to docs tests
+  - Propose improvements to the Kubernetes website or other tooling
+
+{{% /capture %}}