SNICallback native

Hello, I would like to indicate a new native functionality for express in your next updates: native **SNICallback**.

Today we do not have native support for such functionality. I myself, in a current project, needed SNICallback and I only found it in NodeJS native https functions but I didn't find any direct implementation in ExpressJS where I would rather have a raised server.

The solution was to join NodeJS https together with Express to use such a feature, but if the same feature was available natively in Express it would be of great help.

Such functionality is important because it helps us a lot in several things, including leaving a Dynamic SSL (which was for this functionality I needed).

Explanation of functionality in NodeJS can be found at the link: [SNICallback in NodeJS](https://nodejs.org/dist/latest-v16.x/docs/api/tls.html#tlscreatesecurecontextoptions)