UXP/devtools/client/aboutdebugging/test/addons/test-devtools-webextension/manifest.json

{
  "manifest_version": 2,
  "name": "test-devtools-webextension",
  "version": "1.0",
  "applications": {
    "gecko": {
      "id": "test-devtools-webextension@mozilla.org"
    }
  },
  "background": {
    "scripts": ["bg.js"]
  },
  "browser_action": {
    "default_title": "WebExtension Popup Debugging",
    "default_popup": "popup.html"
  }
}