Welcome: Wrap await code in async IIFE (#87)

* Welcome: Wrap await code in async IIFE

* Update content/welcome.mdx

Co-authored-by: Charmander <~@charmander.me>

Co-authored-by: Charmander <~@charmander.me>

Author: anishkny

content/welcome.mdx

@@ -34,11 +34,13 @@ This is the simplest possible way to connect, query, and disconnect with async/a
 const { Client } = require('pg')
 const client = new Client()
 
-await client.connect()
+;(async () => {
+  await client.connect()
 
-const res = await client.query('SELECT $1::text as message', ['Hello world!'])
-console.log(res.rows[0].message) // Hello world!
-await client.end()
+  const res = await client.query('SELECT $1::text as message', ['Hello world!'])
+  console.log(res.rows[0].message) // Hello world!
+  await client.end()
+})()
 ```
 
 And here's the same thing with callbacks: