Github: Commit preview documentation

[smashwilson]

This is a checklist of the documentation we'd like to have in place before we ship an Atom release that includes the Commit Preview feature we're introducing in #1767.

Documentation

• [x] Gif for demos
• [x] Flight manual update https://github.com/atom/flight-manual.atom.io/pull/499
• [x] README image update https://github.com/atom/github/pull/1810
• [x] Feature blog post on GitHub blog
• [x] "Notable Change" sentence for Atom release notes
• [x] Release blurb for Atom release blog post https://github.com/atom/blog.atom.io/pull/245
• [x] Tweet

[smashwilson]

@simurai when you have bandwidth, could you tackle the .gif creation and README screenshot updates? 🙇

[simurai]

I think it's probably safest to only start with this once #1767 is merged and we have some sort of "feature freeze". Otherwise we have to do everything twice like if "the button" would still move or so.

The release date: Nov 28.

This will be a great testrun for Atom's release assets Figma file.

[simurai]

Gif for demos

@sguthals Sorry 😇, I already forgot in what repo these ☝️ gifs go?

[simurai]

Let's close this again. Tweet will be in the next Atom release. I also added the demo gif to https://github.com/atom/github/pull/1767 at the top.

[annthurium]

we're still waiting on @meaghanlewis who has agreed to write a blog post for this in January when the feature rolls over into stable, so let's keep that open until then.