firebase.json

{
   "hosting":{
    "public":"build",
    "ignore":[
       "firebase.json",
       "**/.*",
       "**/node_modules/**"
    ],
    "rewrites": [
      {
        "source": "**",
        "function": "host"
      }
    ],
    "headers": [ {
      "source" : "**/*.@(eot|otf|ttf|ttc|woff|woff2|font.css)",
      "headers" : [ {
        "key" : "Access-Control-Allow-Origin",
        "value" : "*"
      } ]
    }, {
      "source" : "**/*.@(js*|css*|jpg*|jpeg*|gif*|png*|ico)",
      "headers" : [ {
        "key" : "Cache-Control",
        "value" : "max-age=604800"
      } ]
    }, {
      "source" : "404.html",
      "headers" : [ {
        "key" : "Cache-Control",
        "value" : "max-age=300"
      } ]
    } ]
   },
   "functions":{
    "predeploy":[
      "npm --prefix \"$RESOURCE_DIR\" run lint"
    ],
    "source":"functions"
   }
}