feature request: enable CORS for the pub.dev API

[csells]

The community has built a pretty great dart wrapper around the pub.dev API: the pub_api_client package. And it works great everywhere except from the web. I wonder if we could configure the CORS settings for Flutter Web use of the pub.dev API?

tagging @jonasfj. thanks!

[jonasfj]

I think that for GET requests setting some decent CORS headers should be okay.