Vary nginx cache by wporg_locale cookie value

This cookie gets set by the locale-detection pluginPlugin A plugin is a piece of software containing a group of functions that can be added to a WordPress website. They can extend functionality or add new features to your WordPress websites. WordPress plugins are written in the PHP programming language and integrate seamlessly with WordPress. These can be free in the WordPress.org Plugin Directory https://wordpress.org/plugins/ or can be cost-based plugin from a third-party, which is used on the login site, and soon on the Learn WordPress site. In the case of Learn, the value of this cookie will determine the language that is displayed in the front end UIUI UI is an acronym for User Interface - the layout of the page the user interacts with. Think ‘how are they doing that’ and less about what they are doing. of the site (see this PR). Caching the pages without consideration of the chosen locale has a lot of potential for bad UXUX UX is an acronym for User Experience - the way the user uses the UI. Think ‘what they are doing’ and less about how they do it..

Could we update the nginxNGINX NGINX is open source software for web serving, reverse proxying, caching, load balancing, media streaming, and more. It started out as a web server designed for maximum performance and stability. In addition to its HTTP server capabilities, NGINX can also function as a proxy server for email (IMAP, POP3, and SMTP) and a reverse proxy and load balancer for HTTP, TCP, and UDP servers. https://www.nginx.com/. config to take this cookie into account when caching wporg pages? This locale switching functionality is intended for use on various wp.org sites beyond just Learn, so ideally this change would apply for *.wordpress.org

#prio1 because we’d like to get the locale switcher launched on the Learn site soon.

Bumping this down to #prio2 as it was worked around, but needs a call on whether this should just be closed or not.