Update docs to use `standalone`

[timdeschryver]

With standalone become more mainstream and the default, I think we should update the docs pages to reflect this change.

I can help with the migration, but I wanted to verify if this is OK.

[FabianGosebrink]

Sure, this is fine. Thanks. Should we erase the module related things completely from the docs?

[timdeschryver]

That's a call you can make, for the NgRx docs we added a note about NgModules with a reference to the archived docs (e.g. https://v17.ngrx.io/docs). For now we can also add a standalone and NgModules snippet (for the API docs that don't have them), but put the standalone version first.