Update icon

[mit-mit]

Dart has a new icon, so we should update the Pub site. If possible, we should also tweak the color scheme to match the new colors.

[isoos]

@mit-mit: I was not able to find a reference to a logo-only (no "Dart" text) SVG image. (Also: https://github.com/dart-lang/logos is outdated)

[mit-mit]

I'll have the icons for you on Monday!

For now, can you look the colors? Here they are:

• Regular blue: #02589B
• Contrast/highlight color: #41C4FF

[anders-sandholm]

Looks like this has been fixed, landed, and deployed.
Woohoo.
Thanks @isoos and @jakobr-google

[mit-mit]

Re-opening: there is still an issue with font sizes we are tracking down, so this is not entirely fixed