Stub out deprecation files

[jenweber]

We need to create these files ASAP so that the source code has something to link to. It was discussed & planned at the last learning team meeting that we would create and ship placeholder files ASAP.

We still need volunteers to fill in the actual content. For the files that have a writeup, it's just copy-pasted from the deprecation message, and we need to give more guidance than that.

If you can help out, please see #893 Thank you!

[jenweber]

@locks do you know what the version numbers should be, if the "since" was never filled in? Should some of these deprecations be in the 3.x folder instead, or should I just label them all since: 4.0.0?

[locks]

I don't think any of them are v4 deprecations, but let's discuss together in the call!

[jenweber]

This file should be deleted. We already have an entry: https://deprecations.emberjs.com/v3.x#toc_ember-built-in-components-legacy-arguments

And a PR: emberjs/ember.js#19747

[jenweber]

What should these versions be? See PR emberjs/ember.js#19748 and emberjs/ember.js#19748

[jenweber]

To-do:

• Remove files for entries that already have PRs
• Apply the version updates
• Add a link to the WIP entries inviting people to help edit
• Put in a sentence here & there if I can find one

Followup steps:

• Ask the deprecation contributor/RFC author if they will help write these. Share the context that deprecation guides are supposed to be written before releases finish.