Update and ensure consistency in demo files

[killerwolf]

Background

The README.md lists demos that don't precisely match the actual demo directory contents. Additionally, the demo files should be reviewed to ensure they all work correctly, especially after dependency updates and other changes are implemented.

Current Demo Directory Contents

basic-usage.html
custom-config.html
demo-esm.html
demo-umd.html
index-local.html
index.html
preact-importmap-demo.html
react-integration.jsx
vue-importmap-demo.html
vue-integration.js
favicon.ico
android-chrome-192x192.png

Tasks

1. Update README.md to accurately reflect the available demos
2. Test each demo to ensure it works properly with the current implementation
3. Update any outdated framework integration examples (especially the Vue example that is using Vue 2 syntax)
4. Ensure demos follow best practices and match library's API
5. Update any demos that need changes due to the rollup configuration updates or ESM changes
6. Add brief descriptions for each demo in the README to help users find the right example for their needs

Expected Outcome

• All demos working correctly and demonstrating proper usage of the library
• README.md that accurately lists and describes available demos
• Framework integration examples that use current best practices

This addresses item #8 from the review in issue #6.