Github makes own copies of images referenced in README, and that fails for large image sizes. The gif has 6MB and so is over the threshold.
Instead of using an off-GitHub image, use the same image uploaded to user-images.githubusercontent.com. This makes GitHub show the image even when it's very large.
This reverses https://github.com/flutter/flutter/pull/11170 and finalizes https://github.com/flutter/flutter/pull/11158.
Github makes copies of images referenced in README, and it fails for large image sizes. The gif has 6MB and so is over the threshold.
This removes the image until I can figure out how to reinsert it so that it shows.
Reuses flutter.io homepage content to give README.md an upgrade, since this file will be the shop window of Flutter to a large part of newcomers.
The downside is that we now have duplicate content that should be updated in unison with the main site but which cannot be easily copy-pasted, due to constraints of github's Markdown renderer.
