Create package.json to launch back and front

[srioboo]

Use bun to the operations or other equivalent, concurrently need to be installed

{
  "name": "mi-monorepo",
  "private": true,
  "workspaces": [
    "backend",
    "frontend"
  ]
}

{
  "scripts": {
    "start:backend": "cd backend && ./mvnw spring-boot:run",
    "start:frontend": "cd frontend && npm start",
    "start": "concurrently \"yarn start:backend\" \"yarn start:frontend\""
  }
}