docs: update subscription example

Author: huozhi

examples/subscription/README.md

@@ -0,0 +1,30 @@
+# Subscription
+
+## One-Click Deploy
+
+Deploy your own SWR project with Vercel.
+
+[![Deploy with Vercel](https://vercel.com/button)](https://vercel.com/new/clone?s=https://github.com/vercel/swr/tree/main/examples/subscription)
+
+## How to Use
+
+Download the example:
+
+```bash
+curl https://codeload.github.com/vercel/swr/tar.gz/main | tar -xz --strip=2 swr-main/examples/storage-tab-sync
+cd storage-tab-sync
+```
+
+Install it and run:
+
+```bash
+yarn
+yarn dev
+# or
+npm install
+npm run dev
+```
+
+## The Idea behind the Example
+
+Show how you could use SWR to synchronize localStorage values between tabs.

examples/subscription/package.json

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+{
+  "name": "subscription",
+  "private": true,
+  "license": "MIT",
+  "dependencies": {
+    "next": "latest",
+    "react": "latest",
+    "react-dom": "latest",
+    "swr": "latest"
+  },
+  "scripts": {
+    "dev": "next",
+    "start": "next start",
+    "build": "next build"
+  }
+}