firebase.json

{
  "hosting": {
    "public": "build",
    "ignore": ["firebase.json", "**/.*", "**/node_modules/**"],
    "rewrites": [
      {
        "source": "/api",
        "function": "api"
      },
      {
        "source": "**",
        "destination": "/index.html",
        "headers": [
          {
            "key": "Access-Control-Allow-Origin",
            "value": "*"
          }
        ]
      }
    ],
    "headers": [
      {
        "source": "**/*.@(eot|otf|ttf|ttc|woff|font.css)",
        "headers": [
          {
            "key": "Access-Control-Allow-Origin",
            "value": "*"
          }
        ]
      },
      {
        "source": "**/*.@(jpg|jpeg|gif|png)",
        "headers": [
          {
            "key": "Cache-Control",
            "value": "max-age=604800, s-maxage=3600"
          },
          {
            "key": "Access-Control-Allow-Origin",
            "value": "*"
          }
        ]
      }
    ]
  },
  "functions": {
    "predeploy": [
      "yarn --cwd \"$RESOURCE_DIR\" install",
      "npm --prefix \"$RESOURCE_DIR\" run lint",
      "npm --prefix \"$RESOURCE_DIR\" run build"
    ],
    "source": "functions"
  },
  "emulators": {
    "functions": {
      "port": 5001
    },
    "firestore": {
      "port": 8080
    },
    "hosting": {
      "port": 5000
    },
    "ui": {
      "enabled": true
    }
  }
}