Confirmation prompt in onDestroy doesn't actually work.

[yongrenjie]

demoland-web/web/src/lib/leftSidebar/Create.svelte

Lines 45 to 50 in 9347894

	// Prompt user to confirm if they navigate away from this tab
	onDestroy(() => {
	if (userChangesPresent && window.confirm(userChangesPromptText)) {
	changes = new Map();
	}
	});

Even if the user doesn't press confirm, it doesn't actually stop the component from being destroyed. Need to find some other way to 'interrupt' the process

Could have some custom logic in Tabs.svelte, but that feels pretty ugly.