update: Flow instance provides update node internals func

* Rename onLoadParams to FlowInstance
* Pass update node internals to instance

examples/UpdateNodeInternals/UpdateNodeInternalsExample.vue

@@ -0,0 +1,77 @@
+<script lang="ts" setup>
+import { CSSProperties } from 'vue'
+import CustomNode from './CustomNode.vue'
+import Flow, {
+  NodeType,
+  addEdge,
+  useZoomPanHelper,
+  Node,
+  Elements,
+  Connection,
+  Edge,
+  ElementId,
+  Position,
+  isEdge,
+  FlowInstance,
+} from '~/index'
+
+const initialHandleCount = 1
+
+const initialElements: Elements = [
+  {
+    id: '1',
+    type: 'custom',
+    data: { label: 'Node 1', handleCount: initialHandleCount, handlePosition: 0 },
+    position: { x: 250, y: 5 },
+  },
+] as Elements
+
+const buttonWrapperStyles: CSSProperties = { position: 'absolute', right: 10, top: 10, zIndex: 10 }
+
+const nodeTypes: Record<string, NodeType> = {
+  custom: CustomNode as NodeType,
+}
+
+let id = 5
+const getId = (): ElementId => `${id++}`
+
+const elements = ref<Elements>(initialElements)
+const flowInstance = ref<FlowInstance>()
+const onConnect = (params: Connection | Edge) => (elements.value = addEdge(params, elements.value))
+const { project } = useZoomPanHelper()
+
+const onPaneClick = (evt: MouseEvent) =>
+  (elements.value = elements.value.concat({
+    id: getId(),
+    position: project({ x: evt.clientX, y: evt.clientY - 40 }),
+    data: { label: 'new node' },
+    targetPosition: Position.Left,
+    sourcePosition: Position.Right,
+  } as Node))
+
+const toggleHandleCount = () =>
+  (elements.value = elements.value.map((el) => {
+    if (isEdge(el)) {
+      return el
+    }
+
+    return { ...el, data: { ...el.data, handleCount: el.data?.handleCount === 1 ? 2 : 1 } }
+  }))
+
+const toggleHandlePosition = () =>
+  (elements.value = elements.value.map((el) => {
+    if (isEdge(el)) return el
+    return { ...el, data: { ...el.data, handlePosition: el.data?.handlePosition === 0 ? 1 : 0 } }
+  }))
+
+const onLoad = (instance: FlowInstance) => (flowInstance.value = instance)
+</script>
+<template>
+  <Flow :elements="elements" :node-types="nodeTypes" @connect="onConnect" @pane-click="onPaneClick" @load="onLoad">
+    <div :style="buttonWrapperStyles">
+      <button @click="toggleHandleCount">toggle handle count</button>
+      <button @click="toggleHandlePosition">toggle handle position</button>
+      <button @click="() => flowInstance.updateNodeInternals('1')">update node internals</button>
+    </div>
+  </Flow>
+</template>