refactor(svelte): cleanup useSvelteFlow, add functions (#3474)

* chore(svelte) removed nodes, edges from useSvelteFlow

* feat(svelte) added deleteElements to useSvelteFlow

* fix(svelte) parent div gets resized correctly, got rid of getBoundingClient Rect

* feat(svelte) added screenToFlowCoordinate

* feat(svelte) added flowToScreenCoordinate to useSvelteFlow

* chore(svelte) removed project from useSvelteFlow

* Delete examples/svelte/src/routes/add-node-on-drop/+server.ts

---------

Co-authored-by: Moritz Klack <info@moritzklack.com>

examples/svelte/src/components/Header/Header.svelte

@@ -15,7 +15,8 @@
 		'two-way-viewport',
 		'usesvelteflow',
 		'useupdatenodeinternals',
-		'validation'
+		'validation',
+		'add-node-on-drop'
 	];
 
 	const onChange = (event: Event) => {