firebase.json

{
  "firestore": {
    "rules": "firestore.rules",
    "indexes": "firestore.indexes.json"
  },
  "functions": {
    "predeploy": [
      "npm --prefix \"$RESOURCE_DIR\" run lint"
    ],
    "source": "functions"
  },
  "hosting": {
    "public": "build",
    "ignore": [
      "firebase.json",
      "**/.*",
      "**/node_modules/**"
    ],
    "rewrites": [
      {
        "source": "api/**",
        "function": "api"
      }
    ],
    // "redirects": [
    //   {
    //     "source": "/api/*",
    //     "destination": "https://firebase.google.com",
    //     "type": 302
    //   }
    // ]
    "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=7200"
      } ]
      }, {
      "source" : "404.html",
      "headers" : [ {
        "key" : "Cache-Control",
        "value" : "max-age=300"
      } ]
    } ]
    // "cleanUrls": true,
    // "trailingSlash": false
  }
}