feat(templates): add vercel postgres template (#7841)

- docs: add db-vercel-postgres info
- feat: update template variations

docs/configuration/overview.mdx

@@ -36,7 +36,6 @@ Here is one of the simplest possible Payload configs:
 ```ts
 import { buildConfig } from 'payload'
 import { mongooseAdapter } from '@payloadcms/db-mongodb'
-// import { postgresAdapter } from '@payloadcms/db-postgres'
 
 export default buildConfig({
   secret: process.env.PAYLOAD_SECRET,