use new sourcegraphstatic.com host for static assets
Created by: sqs
The https://sourcegraphstatic.com site serves content from the sourcegraph-assets
Google Cloud Storage bucket. We are using this hostname instead of https://storage.googleapis.com/sourcegraph-assets/ because the latter is blocked by some ad blockers, which means our assets are not visible to many of our users.
fastmod https://storage.googleapis.com/sourcegraph-assets/ https://sourcegraphstatic.com/
Related PR: https://github.com/sourcegraph/about/pull/1252