Examine source code of Feed Preview

{
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "version": "14",
  "description": "__MSG_extensionDescription__",
  "author": "Guido Berhoerster",
  "homepage_url": "https://code.guido-berhoerster.org/addons/firefox-addons/feed-preview/",
  "default_locale": "en",
  "applications": {
    "gecko": {
      "id": "feed-preview@code.guido-berhoerster.org",
      "strict_min_version": "60.0"
    }
  },
  "icons": {
    "48": "icons/feed-preview-48.png",
    "96": "icons/feed-preview-96.png"
  },
  "permissions": [
    "storage",
    "tabs",
    "http://*/*",
    "https://*/*",
    "webRequest",
    "webRequestBlocking"
  ],
  "background": {
    "page": "background.html"
  },
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*",
        "file:///*"
      ],
      "js": [
        "content_scripts/feed-probe.js"
      ],
      "run_at": "document_end"
    }
  ],
  "web_accessible_resources": [
    "web_resources/xhtml-to-html.xsl",
    "web_resources/images/*.svg",
    "web_resources/style/*.css"
  ],
  "page_action": {
    "browser_style": true,
    "default_icon": "icons/feed-preview-action.svg",
    "default_title": "Feeds",
    "default_popup": "popup/feed-selection.html"
  },
  "options_ui": {
    "page": "options/options.html",
    "browser_style": true
  }
}