enable links to sections of the API docs

[annastuchlik]

Refs scylladb/scylladb#20065
Details scylladb/scylladb#20065 (comment)

This method of defining references to anchors may cause issues with multiversion support, as it requires adding the current version (latest or branch name) to the link.

The solution is to create a custom role to support cross-references to anchors in pages that NOT generated with Markdown or reStructuredText, like the API references. I’ve added this to my to-do list.