Add flexible tagName support to PanelProps

[in-ch]

related to (#407)

Instead of fixing the tagName type to keyof HTMLElementTagNameMap, it has been made flexible by using a generic type.
This allows TypeScript to better infer event object types like handleDrop when a specific tagName is provided in the component.

<Panel
    onDrop={(e: DragEvent<HTMLDivElement>) => {
      if (e.currentTarget.contains(e.relatedTarget)) return;
    }}
    className={styles.PanelRow}
    defaultSize={20}
    minSize={10}
    tagName="div"
  >
    <div className={styles.Centered}>left</div>
</Panel>

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Name	Status	Preview	Comments	Updated (UTC)
react-resizable-panels	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 27, 2024 0:19am

[bvaughn]

I like this approach!