Make other specs more discoverable from the main javadoc pages

The other specs for a JDK release, available at [1] aren't reachable from the Javadoc pages. It would be really nice to make them reachable, therefore discoverable, from the Javadoc pages.

Options are to:

1 - Include a link to [1] from the Index page - Not super ideal

2 - Include a link to [1] from the Overview page - Nice idea

3 - What about including another top-level tab ? Possibly between Deprecated and Index, thats say 'Other Specs' or just 'Specs', that may be even more easily discoverable.

[1] https://docs.oracle.com/en/java/javase/19/docs/specs/index.html