build(docs-infra): improve caching configuration for Firebase hosting (#28785)

This will hopefully improve(/fix?) the errors discussed in #28114.
See there for a more detailed discussion.

PR Close #28785

aio/.gitignore

@@ -26,11 +26,13 @@
 !.vscode/extensions.json
 
 # misc
+/.firebase/
 /.sass-cache
 /connect.lock
 /coverage
 /libpeerconnection.log
 debug.log
+firebase-debug.log
 npm-debug.log
 testem.log
 /typings

aio/firebase.json

@@ -120,12 +120,25 @@
     ],
     "headers": [
       {
-        "source": "/",
+        // All paths (URLs without a file extension).
+        "source": "**/!(*.*)",
         "headers": [
-          {
+          {"key": "Cache-Control", "value": "no-cache"},
-            "key": "Link",
+          {"key": "Link", "value": "</generated/navigation.json>;rel=preload;as=fetch,</generated/docs/index.json>;rel=preload;as=fetch"}
-            "value": "</generated/navigation.json>;rel=preload;as=fetch,</generated/docs/index.json>;rel=preload;as=fetch"
+        ]
-          }
+      },
+      {
+        // Images, fonts, (non-hashed) CSS/JS files.
+        "source": "**/*.@(gif|jpg|jpeg|png|svg|webp|js|css|eot|otf|ttf|ttc|woff|woff2)",
+        "headers": [
+          {"key": "Cache-Control", "value": "max-age=86400"}  // 1 day
+        ]
+      },
+      {
+        // Hashed CSS/JS files...
+        "source": "**/*.+([0-9a-f]).@(css|js)",
+        "headers": [
+          {"key": "Cache-Control", "value": "max-age=2592000"}  // 30 days
         ]
       }
     ]