mue/src/manifest-firefox.json

{
  "manifest_version": 2,
  "name": "Mue",
  "version": "0.1",
  "browser_action": {
    "default_icon": "./assets/img/icon.png"
  },
  "chrome_url_overrides": {
    "newtab": "index.html"
  },
  "chrome_settings_overrides": {
    "homepage": "index.html"
  }
}