Add run on Google Cloud Run button to the docker example (#25824)

## Documentation / Examples

- [x] Make sure the linting passes


### Deployed with Cloud Run Button

<img width="1075" alt="Screen Shot 2021-06-06 at 10 22 51 pm" src="https://user-images.githubusercontent.com/170554/120924210-d7946780-c715-11eb-889e-79679f795c54.png">

### Next.js working on Google Cloud Run

<img width="982" alt="Screen Shot 2021-06-06 at 10 23 10 pm" src="https://user-images.githubusercontent.com/170554/120924229-e418c000-c715-11eb-9aca-569923f7306d.png">

examples/with-docker/.gitignore

@@ -32,3 +32,7 @@ yarn-error.log*
 
 # vercel
 .vercel
+
+# lock files
+yarn.lock
+package-lock.json

examples/with-docker/README.md

@@ -34,6 +34,10 @@ The `start` script in `package.json` has been modified to accept a `PORT` enviro
    - You will be prompted for [region](https://cloud.google.com/run/docs/quickstarts/build-and-deploy#follow-cloud-run): select the region of your choice, for example `us-central1`.
    - You will be prompted to **allow unauthenticated invocations**: respond `y`.
 
+Or click the button below, authorize the script, and select the project and region when prompted:
+
+[![Run on Google Cloud](https://deploy.cloud.run/button.svg)](https://deploy.cloud.run/?git_repo=https://github.com/vercel/next.js.git&dir=examples/with-docker)
+
 ## Running Locally
 
 First, run the development server:

examples/with-docker/app.json

@@ -0,0 +1,10 @@
+{
+  "name": "nextjs",
+  "options": {
+    "allow-unauthenticated": true,
+    "memory": "256Mi",
+    "cpu": "1",
+    "port": 3000,
+    "http2": false
+  }
+}

examples/with-docker/pages/index.js

@@ -11,7 +11,7 @@ export default function Home() {
 
       <main className={styles.main}>
         <h1 className={styles.title}>
-          Welcome to <a href="https://nextjs.org">Next.js!</a>
+          Welcome to <a href="https://nextjs.org">Next.js</a> on Docker!
         </h1>
 
         <p className={styles.description}>