Feat(nodes): add initialWidth and initialHeight (#3953)

* feat(react/svelte): add initialWidth/initialHeight closes #3793

* chore(packages): update changelogs

examples/astro-xyflow/src/components/SvelteFlowInitialExample/CustomNode.svelte

@@ -0,0 +1,25 @@
+<script lang="ts">
+  import { Handle, Position, type NodeProps } from '@xyflow/svelte';
+
+  type $$Props = NodeProps;
+
+  let text = 'some default text';
+</script>
+
+<Handle type="target" position={Position.Left} />
+<div class="custom">
+  <div>
+    text: {text}
+  </div>
+  <input type="text" bind:value={text} />
+</div>
+<Handle type="source" position={Position.Right} />
+
+<style>
+  .custom {
+    background-color: white;
+    padding: 10px;
+    border: 1px solid #777;
+    border-radius: 20px;
+  }
+</style>

examples/astro-xyflow/src/components/SvelteFlowInitialExample/index.svelte

@@ -0,0 +1,39 @@
+<script lang="ts">
+  import { writable } from 'svelte/store';
+  import { SvelteFlow, Controls, Background, BackgroundVariant, type Node, type Edge } from '@xyflow/svelte';
+
+  import '@xyflow/svelte/dist/style.css';
+  import CustomNode from './CustomNode.svelte';
+
+  const nodes = writable<Node[]>([
+    {
+      id: '1',
+      position: { x: 0, y: 0 },
+      data: {},
+      initialWidth: 100,
+      initialHeight: 40,
+      type: 'input-node',
+    },
+    {
+      id: '2',
+      position: { x: 0, y: 150 },
+      data: {},
+      initialWidth: 100,
+      initialHeight: 40,
+      type: 'input-node',
+    },
+  ]);
+
+  const edges = writable<Edge[]>([{ id: '1-2', source: '1', target: '2' }]);
+
+  const nodeTypes = {
+    'input-node': CustomNode,
+  };
+</script>
+
+<div style="height: 400px; width: 700px;">
+  <SvelteFlow {nodes} {edges} {nodeTypes} fitView width={700} height={400}>
+    <Controls />
+    <Background variant={BackgroundVariant.Dots} />
+  </SvelteFlow>
+</div>