[Documentation] [5.x] New Async Functionality Missing From Docs

[xjamundx]

The API docs here:
https://expressjs.com/en/5x/api.html

And the migration guide:
https://expressjs.com/en/guide/migrating-5.html

Both currently fail to mention the killer feature of express 5, which is async/promise support middleware and routes.

Some of this might be expressjs/express#4321 didn't ship yet, but either way, happy to start a PR with documentation changes reflecting the update. Please let me know if that would be appreciated.

[mgncodes]

Hi, I would like to contribute to this issue. Could you please assign this to me?
Thanks!

[euoia]

For anyone following this issue, the documentation is in the expressjs.com repository: https://github.com/expressjs/expressjs.com

The API docs are here:
https://github.com/expressjs/expressjs.com/tree/gh-pages/_includes/api/en/5x

The migration guide is here:
https://github.com/expressjs/expressjs.com/blob/gh-pages/en/guide/migrating-5.md

[euoia]

I have made a start on a pull request to update the documentation: #1315