docs(site): redirect /quickstart and /installation short paths

Users following abbreviated links guess /docs/quickstart and
/docs/installation and hit raw GitHub-Pages 404s — the real pages live
under /docs/getting-started/. Add client redirects for both.

Consumer-onboarding audit finding #1, Aug 2026.

website/docusaurus.config.ts

@@ -92,6 +92,16 @@ const config: Config = {
             from: '/guides/build-a-hermes-plugin',
             to: '/developer-guide/plugins',
           },
+          {
+            // Users guess these short paths from abbreviated links and hit
+            // raw 404s (consumer-onboarding audit finding #1, Aug 2026).
+            from: '/quickstart',
+            to: '/getting-started/quickstart',
+          },
+          {
+            from: '/installation',
+            to: '/getting-started/installation',
+          },
         ],
       },
     ],