Set delay for popup notifications in Timeline view.

- [x] I am on the [latest](https://github.com/ActivityWatch/activitywatch/releases/latest) ActivityWatch version.
- [x] I have searched the issues of this repo and believe that this is not a duplicate.

- **OS name and version**: Ubuntu 20.04.5 LTS
- **ActivityWatch version**: v0.12.0 (rust)

## Describe the bug
Viewing the details of each event in this new version (0.12.0) is quite "annoying" compared to the previous version (0.11.0).

The popup messages kept jumping when I hovered over events and made it harder for me to focus on seeing each event in detail.
Is it possible to set a delay for them?

Any instructions are appreciated.

## To Reproduce

_This gif has a lower fps than the actual Timeline view pop-up notifications._