deprecate Ember.K

[givanse]

deprecate Ember.K according to emberjs/ember.js#14746

rendered view

[cibernox]

It seems a very clear explanation to me. I'll ping someone with merge rights /cc @locks

[locks]

We'd like the explanation to lean much more in the direction of --empty. We think that most people aren't using the chaining property of Ember.K and it's preferable to go with the simpler option.
@givanse could you tweak it a little bit so that it's more "oh, here's the command with the --empty option. P.S. if you're using chaining, there's --return-this"?

[givanse]

PR updated with added emphasis on the --empty flag
https://github.com/givanse/website/blob/d2b6d8d435dd7d156dc7b0e0c83b3af45f984651/source/deprecations/v2.x.html.md#emberk thoughts?

[rwjblue]

The changes added here look good (thank you!), but can you add a header above your changes for:

### Deprecations Added in 2.12

(since this deprecation will land in 2.12 which is the current emberjs/ember.js#master branch)

[givanse]

Header added
https://github.com/givanse/website/blob/0053f6e7f5d4556937e0b20dd5ca491c306f90cb/source/deprecations/v2.x.html.md#deprecations-added-in-212

I don't know what to do about the failed deploy/netlify

You don't have access to this build log.

[locks]

@givanse it's not your fault, we're trying it out and all PRs are failing for some reason!