Examine source code of No Feed

{
  "manifest_version": 2,
  "name": "No Feed",
  "version": "0.4.0",
  "description": "Hide feed on the most popular social networks",
  "homepage_url": "https://github.com/rewkha/firefox-no-feed",
  "icons": {
    "48": "icons/icon.svg"
  },
  "permissions": [
    "storage",
    "*://facebook.com/*",
    "*://youtube.com/*",
    "*://vk.com/*",
    "*://instagram.com/*",
    "*://twitter.com/*"
  ],
  "browser_action": {
    "default_icon": "icons/icon.svg",
    "theme_icons": [
      {
        "light": "icons/icon.svg",
        "dark": "icons/icon-light.svg",
        "size": 19
      }
    ],
    "default_popup": "popup/popup.html",
    "default_title": "No Feed"
  },
  "content_scripts": [
    {
      "matches": [
        "*://facebook.com/*",
        "*://*.facebook.com/*"
      ],
      "js": [
        "cs/fb.js"
      ]
    },
    {
      "matches": [
        "*://youtube.com/",
        "*://*.youtube.com/"
      ],
      "js": [
        "cs/yt.js"
      ]
    },
    {
      "matches": [
        "*://vk.com/*",
        "*://*.vk.com/*"
      ],
      "js": [
        "cs/vk.js"
      ]
    },
    {
      "matches": [
        "*://twitter.com/*",
        "*://*.twitter.com/*"
      ],
      "js": [
        "cs/tw.js"
      ]
    },
    {
      "matches": [
        "*://instagram.com/",
        "*://*.instagram.com/"
      ],
      "js": [
        "cs/in.js"
      ]
    }
  ]
}