Examine source code of Gmail Persistent Sidebar

{
  "manifest_version": 2,
  "name": "Gmail Persistent Sidebar",
  "version": "1.0.0",
  "description": "Keeps email, chat and spaces sidebar always visible.",
  "homepage_url": "https://github.com/icetbr/webext-gmail-persistent-sidebar",
  "author": "icetbr",
  "icons": {
    "16": "icons/16.png",
    "32": "icons/32.png",
    "48": "icons/48.png",
    "96": "icons/96.png",
    "128": "icons/128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "webext-gmail-persistent-sidebar@icetbr"
    },
    "keywords": [
      "userscript",
      "gmail"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://mail.google.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ]
}