Add manifest.json and add install instructions

protected-audience/samples/devtools-extension/index.md

@@ -4,10 +4,16 @@
 
 ## Description
 
-This sample code shows how a Chrome DevTools extension for Protected Audience could be created.
+This sample code shows how a Chrome DevTools extension for Protected Audience could be created. The sample code collects the events and organizes them in separate tables for different auctions.
+
+This is not an officially supported Google product.
 
 See the following files:
 
 - [All code samples](https://github.com/GoogleChromeLabs/trust-safety-demo/tree/main/protected-audience/samples/devtools-extension/src)
 - [`devtools.js`](https://github.com/GoogleChromeLabs/trust-safety-demo/tree/main/protected-audience/samples/devtools-extension/src/devtools.js)
 - [`service-worker.js`](https://github.com/GoogleChromeLabs/trust-safety-demo/tree/main/protected-audience/samples/devtools-extension/src/service-worker.js)
+
+## Instructions
+
+Download the files in the code sample's `/src` folder and [load the unpacked files](https://developer.chrome.com/docs/extensions/get-started/tutorial/hello-world#load-unpacked)

protected-audience/samples/devtools-extension/src/manifest.json

@@ -0,0 +1,12 @@
+{
+  "name": "Devtools - Protected Audience debugger extension demo",
+  "description": "Summarizes Protected Audience debugging events.",
+  "version": "1.0",
+  "manifest_version": 3,
+  "minimum_chrome_version": "123.0.6274.0",
+  "devtools_page": "devtools.html",
+  "permissions": ["debugger"],
+  "background": {
+    "service_worker": "service-worker.js"
+  }
+}