Improve CONTRIBUTING.md

[pangratz]

• add section about prefixing commits, similar to the one in ember.js (added in [DOC] Add section on commit tagging to CONTRIBUTING.md #4244 by @courajs ✨ )
• add ember-twiddles for easier reporting of a bug (setup using pretender) (added in [DOC canary] Updating CONTRIBUTING.md to use ember-twiddle as examples #4716 by @pete-the-pete)
• add note about RFC for requesting a feature instead of opening issue on emberjs/data
  • implement new feature using feature flags (see Improve CONTRIBUTING.md #4238 (comment), added in [DOC] Update CONTRIBUTING.md for feature flags #4327 by @sbatson5)
• add section about tests for assert / warn to use testInDebug so they are skipped when testing in production environment (added in Add note on testInDebug #4240 by @courajs 🚀 )

[courajs]

Can we just copy in the section on commit prefixing (and credit at the end)? Are there any differences?

[pangratz]

Can we just copy in the section on commit prefixing (and credit at the end)? Are there any differences?

They are basically the same. I think it is ok to copy them (cc @rwjblue @bmac).

[courajs]

• Add section about wrapping new feature work in a feature flag (?)

This should include:

• importing isEnabled
• wrapping feature code
• wrapping new tests
• adding to features.json
• adding to FEATURES.md
• how to run tests with the feature enabled

I figured this out by looking up a merged [FEATURE] PR #4110

[pete-the-pete]

can someone describe the work involved with?:

• add ember-twiddles for easier reporting of a bug (setup using pretender)

[courajs]

@pete-the-pete I believe this involves updating the jsbins/jsfiddle linked in Reporting a Bug to

• Use ember twiddle instead of jsbin/fiddle
• Use pretender instead of mockjax

Although I'd ask @pangratz to weigh in on why pretender is a better choice than mockjax - it's not obvious to me.

[dan-ste]

@pangratz There is still need help? I'm a beginner in OSS and want to make my first PR :)

[wecc]

From #4362 re Ember Twiddle:

The reporting a bug section has js bins etc but Ember Twiddle can be alot easier to use. @pangratz had a basic one https://ember-twiddle.com/0e1a24aabb8fa7c1fdd8/copy?fileTreeShown=false&numColumns=2&openFiles=routes.application.js%2Ctemplates.application.hbs that I found easy to play with and add to.