Examine source code of Emoji Everywhere

{
  "manifest_version": 2,
  "name": "Emoji Everywhere",
  "description": "Replaces :custom_emoji: text on any webpage with custom emojis from Slack workspaces and ZIP imports",
  "version": "0.2.3",
  "icons": {
    "16": "icons/16.png",
    "32": "icons/32.png",
    "48": "icons/48.png",
    "128": "icons/128.png"
  },
  "permissions": [
    "identity",
    "storage",
    "unlimitedStorage",
    "activeTab",
    "tabs",
    "https://slack.com/api/*",
    "https://*.slack-edge.com/*",
    "https://emoji.slack-edge.com/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "emoji-everywhere@extension",
      "data_collection_permissions": {
        "required": [
          "authenticationInfo"
        ],
        "optional": []
      }
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Emoji Everywhere",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_idle",
      "js": [
        "content-scripts/content.js"
      ]
    }
  ]
}