Examine source code of keybr red border

{
  "manifest_version": 2,
  "name": "srcAddon",
  "version": "1.0",
  "description": "Adds a red border to all webpages on srcmake.com",
  "icons": {
    "48": "src48x48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.keybr.com/*"
      ],
      "js": [
        "srcborder.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{816c3874-d88c-4d6e-bc19-0cc44bcfce96}"
    }
  }
}