Add example: Bun HTTP server showcasing jrx JSX-to-JSON rendering

Bun React app with HMR that demonstrates jrx's render() pipeline.
Shows JSX source, live UI via @json-render/react, and JSON output
side by side.

- example/specs/simple.tsx: flat Stack > Text + Button
- example/specs/full.tsx: nested layout with state, events,
  visibility conditions, and watchers
- Uses defineCatalog + defineRegistry from @json-render/react
- Fix package.json exports to match actual tsup output (.js/.cjs
  instead of .mjs/.js)

Co-authored-by: Ona <no-reply@ona.com>

example/components.ts

@@ -0,0 +1,23 @@
+import { jsx } from "jrx/jsx-runtime";
+import type { JrxNode } from "jrx";
+
+
+export function Stack(props: Record<string, unknown>): JrxNode {
+  return jsx("Stack", props);
+}
+
+export function Card(props: Record<string, unknown>): JrxNode {
+  return jsx("Card", props);
+}
+
+export function Text(props: Record<string, unknown>): JrxNode {
+  return jsx("Text", props);
+}
+
+export function Button(props: Record<string, unknown>): JrxNode {
+  return jsx("Button", props);
+}
+
+export function Input(props: Record<string, unknown>): JrxNode {
+  return jsx("Input", props);
+}