docs(deploying-to-firebase.md): add firebase.json cache configuration (…

…#21897)

* docs(deploying-to-firebase.md): add firebase.json cache configuration

Adds how to update the `firebase.json` to configure the firebase cache correctly.

* chore: format

Co-authored-by: GatsbyJS Bot <mathews.kyle+gatsbybot@gmail.com>

docs/docs/deploying-to-firebase.md

@@ -45,6 +45,64 @@ In this guide, you will learn how to deploy your Gatsby site to Firebase Hosting
 
    When prompted to select your public directory, press <kbd>enter</kbd>. It will default to `public`, which is also Gatsby's default public directory.
 
+1. Update the `firebase.json` with the following cache settings
+
+```json
+{
+  "hosting": {
+    "public": "public",
+    "ignore": ["firebase.json", "**/.*", "**/node_modules/**"],
+    "headers": [
+      {
+        "source": "**/*",
+        "headers": [
+          {
+            "key": "cache-control",
+            "value": "cache-control: public, max-age=0, must-revalidate"
+          }
+        ]
+      },
+      {
+        "source": "static/**",
+        "headers": [
+          {
+            "key": "cache-control",
+            "value": "public, max-age=31536000, immutable"
+          }
+        ]
+      },
+      {
+        "source": "**/*.@(css|js)",
+        "headers": [
+          {
+            "key": "cache-control",
+            "value": "public, max-age=31536000, immutable"
+          }
+        ]
+      },
+      {
+        "source": "sw.js",
+        "headers": [
+          {
+            "key": "cache-control",
+            "value": "cache-control: public, max-age=0, must-revalidate"
+          }
+        ]
+      },
+      {
+        "source": "page-data/**",
+        "headers": [
+          {
+            "key": "cache-control",
+            "value": "cache-control: public, max-age=0, must-revalidate"
+          }
+        ]
+      }
+    ]
+  }
+}
+```
+
 1. Prepare your site for deployment by running `gatsby build`. This generates a publishable version of your site in the `public` folder.
 
 1. Deploy your site by running the following command: