Examine source code of Override Text Encoding

{
  "manifest_version": 2,
  "name": "Override Text Encoding",
  "short_name": "Charset",
  "version": "1.2",
  "description": "Manually set the charset (character encoding) for a webpage.",
  "homepage_url": "https://github.com/nneonneo/firefox-charset-extension",
  "icons": {
    "48": "icons/extension.svg",
    "96": "icons/extension.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{eac1b56f-f3a7-40f4-9181-557dd6e63bf3}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    },
    "gecko_android": {}
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "storage",
    "<all_urls>"
  ],
  "options_ui": {
    "browser_style": true,
    "page": "options.html"
  },
  "background": {
    "scripts": [
      "common.js",
      "background.js"
    ]
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "16": "icons/button-dark.svg",
      "32": "icons/button-dark.svg"
    },
    "default_title": "Override Text Encoding",
    "default_popup": "popup.html",
    "theme_icons": [
      {
        "light": "icons/button-light.svg",
        "dark": "icons/button-dark.svg",
        "size": 16
      },
      {
        "light": "icons/button-light.svg",
        "dark": "icons/button-dark.svg",
        "size": 32
      }
    ]
  }
}