Upgrade to heroku-22 stack and pin Node.js version to 18.20.5

[brittanysmart]

Stack Upgrade

This PR prepares the application for upgrading from heroku-20 to heroku-22 stack.

Changes

• Set stack to heroku-22 in app.json
• Pin Node.js version to 18.20.5 for consistency across environments
• Update buildpack configuration for heroku-22 compatibility

Testing

• Review App will be created with heroku-22 stack
• Verify application builds and runs correctly
• Confirm all functionality works as expected

Notes

• Heroku-20 EOL is April 30th, 2024
• This upgrade ensures continued security updates and compatibility

Rollback Plan

If issues occur:

1. Revert to heroku-20 stack
2. Return to previous Node.js version configuration

📦 Published PR as canary version: 0.1.87--canary.332.a46dfe5c330bc20178b5692c94e5ab426a9eddfe.0

✨ Test out this PR locally via:

npm install @knapsack-cloud/public-demo-design-tokens@0.1.87--canary.332.a46dfe5c330bc20178b5692c94e5ab426a9eddfe.0
npm install @knapsack-cloud/public-demo-react@0.1.87--canary.332.a46dfe5c330bc20178b5692c94e5ab426a9eddfe.0
npm install @knapsack-cloud/public-demo-styles@0.1.87--canary.332.a46dfe5c330bc20178b5692c94e5ab426a9eddfe.0
npm install @knapsack-cloud/public-demo-web-components@0.1.87--canary.332.a46dfe5c330bc20178b5692c94e5ab426a9eddfe.0
# or 
yarn add @knapsack-cloud/public-demo-design-tokens@0.1.87--canary.332.a46dfe5c330bc20178b5692c94e5ab426a9eddfe.0
yarn add @knapsack-cloud/public-demo-react@0.1.87--canary.332.a46dfe5c330bc20178b5692c94e5ab426a9eddfe.0
yarn add @knapsack-cloud/public-demo-styles@0.1.87--canary.332.a46dfe5c330bc20178b5692c94e5ab426a9eddfe.0
yarn add @knapsack-cloud/public-demo-web-components@0.1.87--canary.332.a46dfe5c330bc20178b5692c94e5ab426a9eddfe.0