This PR updates the docs and examples for `create-next-app` to include pnpm usage.
The following script was used to update every example README:
```js
const fs = require('fs')
const examples = fs.readdirSync('./examples')
for (let example of examples) {
const filename = `./examples/${example}/README.md`
const markdown = fs.readFileSync(filename, 'utf8')
const regex = new RegExp(`^yarn create next-app --example (.*)$`, 'gm')
const output = markdown.replace(regex, (yarn, group) => {
const pnpm = `pnpm create next-app -- --example ${group}`
return `${yarn}\n# or\n${pnpm}`
})
fs.writeFileSync(filename, output)
}
```
