Simplify and convert with-vercel-fetch example to TypeScript (#43403)

Simplified the example to just the specific feature, and converted to TypeScript.

- `node-fetch@2` is either polyfilled by Next.js or a peerDep of `@vercel/fetch`, I can't quite tell, but either way it can be removed from the dependencies.

## Documentation / Examples

- [X] Make sure the linting passes by running `pnpm build && pnpm lint`
- [X] The "examples guidelines" are followed from [our contributing doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)

examples/with-vercel-fetch/github.d.ts

@@ -0,0 +1,10 @@
+// For simplicity we are creating our own types here.
+// If you want the full types check out:
+// https://github.com/octokit/openapi-types.ts
+export type Repository = {
+  id: number
+  name: string
+  full_name: string
+  stargazers_count: number
+  private: boolean
+} & Record<string, unknown>

examples/with-vercel-fetch/package.json

@@ -6,11 +6,15 @@
     "start": "next start"
   },
   "dependencies": {
-    "@vercel/fetch": "6.1.0",
+    "@vercel/fetch": "^6.2.0",
     "next": "latest",
-    "node-fetch": "2.6.7",
     "react": "^18.2.0",
-    "react-dom": "^18.2.0",
-    "unfetch": "4.2.0"
+    "react-dom": "^18.2.0"
+  },
+  "devDependencies": {
+    "@types/node": "^18.11.9",
+    "@types/react": "^18.0.25",
+    "@types/react-dom": "^18.0.9",
+    "typescript": "^4.9.3"
   }
 }

examples/with-vercel-fetch/pages/index.tsx

@@ -0,0 +1,21 @@
+import type { InferGetStaticPropsType } from 'next'
+import type { Repository } from '../github'
+import createFetch from '@vercel/fetch'
+
+export async function getStaticProps() {
+  const fetch = createFetch()
+  const res = await fetch('https://api.github.com/repos/vercel/next.js')
+  const repo = (await res.json()) as Repository
+
+  return { props: { stars: repo.stargazers_count } }
+}
+
+export default function HomePage({
+  stars,
+}: InferGetStaticPropsType<typeof getStaticProps>) {
+  return (
+    <div>
+      <p>Next.js has {stars} ⭐️</p>
+    </div>
+  )
+}

examples/with-vercel-fetch/tsconfig.json

@@ -0,0 +1,20 @@
+{
+  "compilerOptions": {
+    "target": "es5",
+    "lib": ["dom", "dom.iterable", "esnext"],
+    "allowJs": true,
+    "skipLibCheck": true,
+    "strict": true,
+    "forceConsistentCasingInFileNames": true,
+    "noEmit": true,
+    "esModuleInterop": true,
+    "module": "esnext",
+    "moduleResolution": "node",
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "jsx": "preserve",
+    "incremental": true
+  },
+  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx", "github.d.ts"],
+  "exclude": ["node_modules"]
+}