Examine source code of netboard.me

{
  "manifest_version": 2,
  "name": "Netboard.me",
  "description": "Create engaging educational pages.",
  "version": "1.2.0",
  "id": "jid1-Ak7FC2LwJd1URw",
  "icons": {
    "16": "icon.png",
    "32": "icon32.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "permissions": [
    "https://netboard.me/",
    "contextMenus",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "js": [
        "content.js"
      ],
      "matches": [
        "http://*/*",
        "https://*/*"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "jid1-Ak7FC2LwJd1URw@jetpack"
    }
  }
}