docs: redirect for devtools to the corresponding guide (#42152)

Add redirects for Angular DevTools. We have
https://angular.io/guide/devtools as canonical URL, but as a short URL
we use https://angular.io/devtools to make the extension more
discoverable.

PR Close #42152

aio/firebase.json

@@ -133,7 +133,10 @@
       {"type": 301, "source": "/config/tsconfig", "destination": "/guide/typescript-configuration"},
       {"type": 301, "source": "/config/solution-tsconfig", "destination": "https://devblogs.microsoft.com/typescript/announcing-typescript-3-9/#solution-style-tsconfig"},
       {"type": 301, "source": "/config/app-package-json", "destination": "/guide/strict-mode#non-local-side-effects-in-applications"},
-      {"type": 301, "source": "/strict", "destination": "/guide/strict-mode"}
+      {"type": 301, "source": "/strict", "destination": "/guide/strict-mode"},
+
+      // Use discoverable link for Angular DevTools and redirect to the guide page
+      {"type": 301, "source": "/devtools", "destination": "/guide/devtools"}
     ],
     "rewrites": [
       {

aio/ngsw-config.json

@@ -159,6 +159,8 @@
     "!/testing",
     "!/testing/**",
     "!/config/**",
-    "!/strict"
+    "!/strict",
+    "!/devtools",
+    "!/devtools/**"
   ]
 }

aio/tests/deployment/shared/URLS_TO_REDIRECT.txt

@@ -196,3 +196,4 @@
 /start/routing --> /start/start-routing
 /testing --> /guide/testing
 /testing/first-app-tests.html --> /guide/testing
+/devtools --> /guide/devtools