Graph serialisation update - Links & Reroutes (#279)

* nit

* Add LGraph state POCO

Moves last_link_id, last_node_id and creates same for group and reroute

fix import

* Add new serialisation to LGraph

Add LGraph schema 1
Remove reroute from old serialised graph
Remove brittle inherited types
Ensure stale links are not kept when clearing graph

* Add serialisable exports

* Ensure valid LGraph.state during deserialise

src/litegraph.ts

@@ -24,6 +24,7 @@ export { IWidget }
 export { LGraphBadge, BadgePosition }
 export { SlotShape, LabelPosition, SlotDirection, SlotType }
 export { EaseFunction } from "./types/globalEnums"
+export type { SerialisableGraph, SerialisableLLink } from "./types/serialisation"
 
 export function clamp(v: number, a: number, b: number): number {
     return a > v ? a : b < v ? b : v