package.json with npm script and config for webextension, can be addapted for any JS/HTML app or website.

.eslintrc.json

{
    "env": {
        "browser": true,
        "es6": true
    },
    "extends": "eslint:recommended",
    "rules": {
        "indent": [
            "error",
            4
        ],
        "linebreak-style": [
            "error",
            "unix"
        ],
        "quotes": [
            "error",
            "single"
        ],
        "semi": [
            "error",
            "always"
        ]
    }
}

.htmlhintrc

{
  "attr-lowercase": true,
  "attr-no-duplication": true,
  "attr-unsafe-chars": true,
  "attr-value-double-quotes": true,
  "attr-value-not-empty": true
  "doctype-first": true,
  "doctype-html5": true,
  "id-class-value": "dash",
  "id-unique": true,
  "inline-script-disabled": true,
  "inline-style-disabled": true,
  "space-tab-mixed-disabled": "space",
  "spec-char-escape": true,
  "src-not-empty": true,
  "tag-pair": true,
  "tagname-lowercase": true,
  "title-require": false,
}

.stylelintrc

{
  "extends": "stylelint-config-standard"
}

package.json

{
  "name": "my-extension",
  "version": "0.0.1",
  "description": "Super Extension.",
  "main": "index.js",
  "repository": "github:username/my-extension.git",
  "author": "you",
  "license": "MIT",
  "dependencies": {
  },
  "devDependencies": {
    "concurrently": "^3.4.0",
    "eslint": "^3.19.0",
    "eslint-config-google": "^0.7.1",
    "eslint-config-standard": "^10.2.1",
    "eslint-plugin-promise": "^3.5.0",
    "eslint-plugin-standard": "^3.0.1",
    "htmlhint": "^0.9.13",
    "node-sass": "^4.5.2",
    "stylelint": "^7.10.1",
    "stylelint-config-standard": "^16.0.0"
  },
  "scripts": {
    "sass": "node-sass src/scss/main.scss --output src/css --source-map-embed --source-map-contents",
    "watch:sass": "npm run sass -- --watch",
    "lint:js": "eslint --config .eslintrc.json src;",
    "lint:style": "stylelint --config .stylelintrc src/scss/*.scss;",
    "lint:html": "htmlhint --config .htmlhintrc src/**/*.html;",
    "lint": "concurrently --names  lint:html, lint:style, lint:js -p name 'npm run lint:html' 'npm run lint:style' 'npm run lint:js';",
    "zip": "mkdir -p build && zip -r build/myapp.zip ./src/*",
    "build": "lint && npm run sass && npm run zip"
  }
}

First run yarn install or npm install then to build sass simply run npm run sass, to build and watch npm run watch:sass and to run linters npm run lint. You get the idea...