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/test.md

@@ -214,6 +214,16 @@ Common languages used in Kubernetes documentation code blocks include:
 - `xml`
 - `none` (disables syntax highlighting for the block)
 
+### Code blocks containing Hugo shortcodes
+
+To show raw Hugo shortcodes as in the above example and prevent Hugo
+from interpreting them, use C-style comments directly after the `<` and before
+the `>` characters. The following example illustrates this (view the Markdown
+source for this page).
+
+```none
+{{</* codenew file="pods/storage/gce-volume.yaml" */>}}
+```
 
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