Examine source code of R2RM Web Extension

{
  "manifest_version": 2,
  "name": "R2RM Web Extension",
  "version": "1.0",
  "icons": {
    "128": "icon-128.png"
  },
  "browser_action": {
    "default_icon": "icon-128.png",
    "default_popup": "main.html"
  },
  "permissions": [
    "nativeMessaging",
    "activeTab",
    "<all_urls>",
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "style.css",
        "font-awesome.min.css",
        "simple-line-icons.min.css"
      ]
    }
  ],
  "web_accessible_resources": [
    "font-awesome.min.css",
    "style.css",
    "simple-line-icons.min.css"
  ]
}