Improve how screen readers announce dates in HTML annotations export

[acelaya]

We are currently using time elements to render the various dates included in the HTML report.

These elements have an ISO date in the datetime attribute, and their value uses the YYYY-MM-DD hh:mm format.

Some screen readers, like VoiceOver and Orca, do not announce them as dates, and instead they announce a regular sequence of text with dashes (-) and colons (:).

On the other hand, NVDA announces this properly.