Consider adhering to DNT & Sec-GPC

The DNT header is deprecated and the Sec-GPC header isn't well-supported yet. Nevertheless, Firefox actively uses the DNT header when Do not track is enabled and even enables that flag by default in private browsing.

Seeing how we're trying to attract a mostly technical market that cares about things like tracking and GDPR, it seems to me like we'd better adhere to these two headers. Technically, doing so in JS is trivial. Let me know if this is something the foundation has a certain view on.

When DNT or Sec-GPC is enabled, I'd expect the cookie banner to be automatically declined i.e. not shown and no tracking cookies are saved.