Feature Request: Add 'Enter' and 'Leave' Types to NotebookEditorSelectionChangeEvent

[liorshk]

I’m encountering an issue where the NotebookEditorSelectionChangeEvent triggers twice, making it challenging to determine the current selection. Specifically, it seems that the event triggers both for the change "from" a selection and "to" a selection, but without clear differentiation between the two.

Would it be possible to add event types like "leave" or "enter" to better identify the context of each selection change?

[isidorn]

@rebornix might be able to help answer this

[rebornix]

Let's track this in microsoft/vscode#237913