Suggestion: Add basic type guards to code utils

[Sidnioulz]

Hi folks,

Loving your plugin, kudos for releasing it as FOSS! It's such a time saver to have a basic bundler and UI framework integration from the get go!

I'd like to suggest adding type guard functions for common node operations as part of the template, e.g. hasChildren or isComponentNode, to helps folks less familiar with TypeScript not get stuck on a common issue with handling Figma Plugin API data.

// src-code/utils/type-guards.ts
export function isComponentNode(node: BaseNode): node is ComponentNode {
  return node.type === 'COMPONENT';
}

// src-code/code.ts
listenTS("processComponent", async (res) => {
  const node = await figma.getNodeByIdAsync(res.nodeId);

  if (!isComponentNode(node)) {
    throw new Error(`Node ${nodeId} is of type '${node.type}', expected 'COMPONENT'.`)
  }

  // Do things that require a component node here...

  dispatchTS("processComponentCallback", { result: true });
});

I think this is something that could easily grow over time, and would also be easy to adjust and extend, but folks not familiar with type guards would likely greatly benefit from an example.

Thanks!