DOC: Add release date below release details

Issue with current documentation:

In the current documentation of NumPy and SciPy, in the Release Notes, e.g., https://numpy.org/doc/stable/release/2.0.0-notes.html, there are no dates.

I often find myself searching the release notes for a change, particularly when trying to run old code. I would find it very helpful when I could see how old that change is, e.g., 5 years old.

Currently, to find this out, I find the respective release in the Release Notes, and then I look for the date here: https://github.com/numpy/numpy/releases

Idea or request for content:

I am not sure how the release notes are created currently. But if there is an easy way to include the release date somewhere below the title, I think that would be very useful information.