docs: document new feature stages (#16719)

- [x] translate notes to docs
- [x] move to Home > About > Feature Stages
- [x] decide on bullet point summaries (👍 👎  in comment)

### OOS for this PR

add support page that describes how users can get support. currently,
[this help
article](https://help.coder.com/hc/en-us/articles/25308666965783-Get-Help-with-Coder)
is the only thing that pops up and includes that `Users with valid Coder
licenses can submit tickets` but doesn't show how, nor does it include
the support bundle docs (link or content). it'd be good to have these
things relate to each other

## preview


[preview](https://coder.com/docs/@feature-stages/contributing/feature-stages)

---------

Co-authored-by: EdwardAngert <17991901+EdwardAngert@users.noreply.github.com>
Co-authored-by: Ben Potter <ben@coder.com>

docs/manifest.json

@@ -16,6 +16,11 @@
 					"title": "Screenshots",
 					"description": "View screenshots of the Coder platform",
 					"path": "./start/screenshots.md"
+				},
+				{
+					"title": "Feature stages",
+					"description": "Information about pre-GA stages.",
+					"path": "./about/feature-stages.md"
 				}
 			]
 		},
@@ -639,12 +644,6 @@
 					"path": "./contributing/CODE_OF_CONDUCT.md",
 					"icon_path": "./images/icons/circle-dot.svg"
 				},
-				{
-					"title": "Feature stages",
-					"description": "Policies for Alpha and Experimental features.",
-					"path": "./contributing/feature-stages.md",
-					"icon_path": "./images/icons/stairs.svg"
-				},
 				{
 					"title": "Documentation",
 					"description": "Our style guide for use when authoring documentation",