Add `app.getJumpListSettings()` and `app.setJumpList(callback)` that
make it possible to fully customize the Jump List of an Electron app.
It is now possible to:
- Add tasks to the standard `Tasks` category.
- Add separators to the standard `Tasks` category.
- Add custom categories containing tasks and file links.
- Add system managed Recent/Frequent categories.
- Remove the custom Jump List.
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