Minor version-agnostic page path tweaks (#397)

* Minor version-agnostic page path tweaks

- Adjust the Upcoming Releases page path
- Add the contribution guides
- Add a comment

* Fix version-agnostic page paths

These require an exact match to be deemed version agnostic, so remove
the `contributing/` item and replace it with each page path within the
"Contribute to Teleport Documentation" section.

utils/useVersionAgnosticPages.ts

@@ -1,6 +1,19 @@
 import { getPathWithoutVersion } from "./url";
 
-const agnost = ["preview/upcoming-releases/", "changelog/"];
+// Paths including these segments are version agnostic. If a URL path includes
+// one of these segments when a user visits a page via a navigation link:
+// - The docs site will render the default version of the page
+// - The version switcher will be disabled on the page
+const agnost = [
+  "upcoming-releases/",
+  "changelog/",
+  "contributing/documentation/",
+  "contributing/documentation/reviewing-docs/",
+  "contributing/documentation/issues/",
+  "contributing/documentation/style-guide/",
+  "contributing/documentation/reference/",
+  "contributing/documentation/how-to-contribute/",
+];
 
 export const useVersionAgnosticPages = () => {
   const isVersionAgnosticPage = (route: string) => {