Issue for SuperMixins: Documentations

[JekCharlsonYu]

What: Issue for implementation for Analyzer

FYI on Code ETA : 10/15 in Dart Repo.

For: SuperMixins Implementation and strawman documentation

Meta Issue: This is subsumed under the Super Mixins Meta Issue in the Language Repo

[kwalrath]

Currently, the only thing we could do (not urgent, maybe not even desirable) is update the spec links in the following docs:

https://www.dartlang.org/guides/language/language-tour#adding-features-to-a-class-mixins
https://www.dartlang.org/articles/language/mixins

They currently link to https://github.com/dart-lang/sdk/blob/master/docs/language/informal/mixin-declaration.md, which says that the canonical version of the document is now at https://github.com/dart-lang/language/blob/master/working/0006.%20Super-invocations%20in%20mixins/0007.%20Mixin%20declarations/lrhn-strawman.md.

[kwalrath]

The two links listed in the previous comment have been updated.