[framework] add ember support

[gabrielcsapo]

Issue: #2877

What I did

Added ember framework support

How to test

Is this testable with Jest or Chromatic screenshots?
Does this need a new example in the kitchen sink apps? yes
Does this need an update to the documentation? yes

[ndelangen]

This is super exciting!

[storybook-safe-bot]

	Fails
🚫	PR is not labeled with one of: ["cleanup","BREAKING CHANGE","feature request","bug","documentation","maintenance","dependencies:update","dependencies","other"]

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[rwjblue]

This is essentially the same as how component tests are setup and ran. I'd like to extract a primitive library that can be shared between the main @ember/test-helpers and this project so that we can more easily support broad ranges of Ember applications (and reduce specific coupling in storybook itself).

Thoughts?

[gabrielcsapo]

I totally think this would be something we could decouple. Something like @ember/setup that would just handle setting up and exposing a booted application

[codecov]

Codecov Report

Merging #4237 into master will decrease coverage by 0.49%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master    #4237     +/-   ##
=========================================
- Coverage   40.64%   40.15%   -0.5%     
=========================================
  Files         498      507      +9     
  Lines        5875     5942     +67     
  Branches      785      791      +6     
=========================================
- Hits         2388     2386      -2     
- Misses       3109     3171     +62     
- Partials      378      385      +7

Impacted Files	Coverage Δ
app/ember/src/server/build.js	0% <0%> (ø)
app/ember/src/client/index.js	0% <0%> (ø)
addons/centered/ember.js	0% <0%> (ø)
app/ember/src/server/index.js	0% <0%> (ø)
app/ember/bin/index.js	0% <0%> (ø)
addons/centered/src/ember.js	0% <0%> (ø)
app/ember/src/client/preview/globals.js	0% <0%> (ø)
lib/cli/lib/detect.js	0% <0%> (ø)	⬆️
app/ember/src/server/options.js	0% <0%> (ø)
app/ember/src/client/preview/render.js	0% <0%> (ø)
... and 23 more

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[gabrielcsapo]

@Keraito @ndelangen thoughts on the current state?

[gabrielcsapo]

I updated the example gif and made the stories and intro make more sense in its context. (It used to say go to button and edit, now makes more sense for ember and the welcome-banner example)

[Hypnosphi]

Live example: https://deploy-preview-4237--storybooks-ember.netlify.com

[Hypnosphi]

Can you please add separate commits instead of squashing them each time? Right now it's impossible to review the new diff

[gabrielcsapo]

@Hypnosphi yes I can do that in the future

[igor-dv]

Please also add ember to:

1. https://github.com/storybooks/storybook#supported-frameworks
2. https://storybook.js.org/basics/live-examples

[igor-dv]

why should it be built before using with dev mode?

[gabrielcsapo]

In order to build a storybook you need an ember app to introspect on. It is because of the dynamic nature of ember where as react has an implicit import structure, you can build a component standalone, ember needs to register all components beforehand. Which is why we have the build before dev necessity.

[gabrielcsapo]

@igor-dv added the needed links to #supported-frameworks and live-examples