Feature request: Add `noopener`, `noreferrer`, and `nofollow` to external links

[theborakompanioni]

Have you considered adding rel="noopener noreferrer nofollow" (or a subset) to external links?

• noopener: Instructs the browser to open the link without granting the new browsing context access to the document that opened it [...]. This is especially useful when opening untrusted links, in order to ensure they cannot tamper with the originating document
• noreferrer: revents the browser, when navigating to another page, to send this page address, or any other value, as referrer via the Referer: HTTP header.
• nofollow: Indicates that the linked document is not endorsed by the author of this one, for example if it has no control over it, if it is a bad example or if there is commercial relationship between the two (sold link). This link type may be used by some search engines that use popularity ranking techniques.

target="_blank" already implies noopener for most browsers, but not all, so it might be still good to add it (?).

It might not be a desired behaviour for stackernews (especially noreferrer I can imagine), so if you don't consider adding them (or a subset of them), it's also okay, of course! Let me know what you think.