[Feature Request]: External link indicator

[theletterf]

Prerequisites

• I have searched existing issues to ensure this feature hasn't already been requested
• I have tested using the latest version of docs-builder

What problem are you trying to solve?

When building documentation that features external links, the links should bear an external link indicator. For example:

External link indicators allow users to be aware that they'll exit the docs site. Those links should open in a new tab (_blank) so as not to interrupt the navigation flow.

Proposed Solution

There are several ways of doing this that come to mind. On could be to mark external links with a special CSS class that loads an SVG in the ::after of the link. We might also want to allowlist a set of domains to point out that they are, in fact, Elastic web properties, treating them as internal links.

Examples and Research

Most SSGs for docs have this or are discussing this. Example: squidfunk/mkdocs-material#3595

Alternative Solutions

No response

Additional Context

No response

How important is this feature to you?

Important

[theletterf]

+CC @bmorelli25 @alaudazzi

[bmorelli25]

Those links should open in a new tab (_blank) so as not to interrupt the navigation flow.

This part we've already implemented in #793