Feature : Add 'Time to First/incorporated Review' metric for all pull requests

[meoyushi]

Is your feature request related to a problem?

Right now, while reading through the issues I saw, the action measures Time to First Response, which includes both comment and review.
But for pull requests, a comment surely doesn't always mean that an actual review has been performed.

For repos that follow a structured review workflow, it would be helpful to measure how quickly a pull request receives its first submitted review (approve/request changes) separately from general comment activity.

Describe the solution you'd like

A new metric can be added: 'Time to First Review'

This would measure the duration between pull request creation time and the timestamp when the first review is submitted.

There would be points to be noted:

• Applies only to pull requests
• Respects IGNORE_USERS (like for bots or specific users)
• Is included in summary statistics

Describe alternatives you've considered

If we separate this time from first response time, it would provide more meaningful insight for tracking.

Additional context

I'd be happy to implement this feature if it aligns well.

[zkoppert]

Yes, I think that does align well with what users may want. Feel free to open a pull request with the changes. If you choose not to implement, let me know and I can find time to pick it up.