provide access to highlighted_at

[ddehart]

I see from the Readwise API documentation that highlights have a highlighted_at field and that the highlights/ endpoint supports highlight date filtering.

search_readwise_highlights responses don't appear to include highlight dates, though.

I recently added this MCP to Claude and asked it to summarize highlights within a certain date, and it couldn't fulfill the request due to not having the data. It fell back to this:

I'm still not able to find creation dates for the highlights in the search results. The Readwise API seems to only return content attributes but not metadata like creation dates. Given this limitation, I'll create a table with the highlights that appear to be most recent based on their content and context, focusing on highlights that mention 2025, current events, or recent timeframes

[thiagoghisi]

+1 here! This would unlock many many use cases.

Can I submit a PR with this change?