Describe conditional imports on the 'Libraries' page

[Nashev]

Page URL

https://dart.dev/language/libraries.html

Page source

https://github.com/dart-lang/site-www/tree/main/src/language/libraries.md

Describe the problem

There is not described syntax like
import 'html_stub.dart' if (dart.library.html) 'dart:html' as html;
but i see the source code used it. It must be described there.

P.S. What dart.library.html is here?

Expected fix

Move or copy this section into the https://github.com/dart-lang/site-www/tree/main/src/language/libraries.md page and a little rewrite to more consistency. With a link to specification of the dart.library.

Additional context

No response

[Nashev]

Also there must be link to the https://dart.dev/guides/libraries page for clarification what names can be used in the if part

[atsansone]

@munificent : Would you have something I could reference to write out this documentation?

[parlough]

Thanks for raising this! It's definitely an area we need to work on documenting better soon. We're also open to contributions!

Closing in favor of #4225 which also tracks this work.

Thanks again :)