[feature] Pre-fill time spent with runtime

Description of your request or bug report:

When updating progress on a video item type, it would be nice if clicking on “Add time spent” prefills the slots based on the runtime. The idea being that the time spent is generally a small variation around the runtime (for example, pausing a few times so the actual time spent is runtime + 3 to 5 minutes), and even if it is not a small variation, you get to the real target value faster if you start from the runtime.

It is nothing grandiose and I very well may be the only person making use of the “time spent” in videos but it would be a nice little Quality-of-Life improvement.

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