v1.3.0 - xx chain multi-asset-gating configuration file

• Add sample configuration in NextJS .env for asset-gating with multiple assets and levels (closes #2, it's close enough)
• Add sample code:
  • home page: show settings as JSON and HTML table) on the home page before login
  • auth page: check hard-coded assetId against JSON to show how matching could be done
• Improve documentation