Examine source code of blindify

{
  "browser_action": {
    "default_icon": {
      "48": "icons/yellow-48.png"
    },
    "default_title": "Blindify"
  },
  "applications": {
    "gecko": {
      "id": "blindifywebextension@koduje.pl",
      "strict_min_version": "52.0"
    }
  },
  "permissions": [
    "tabs"
  ],
  "manifest_version": 2,
  "name": "blindify",
  "version": "0.2.1resigned1",
  "description": "Simulates being blind, forcing you to use screen reader to navigate through web",
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Ctrl+Alt+B"
      },
      "description": "Change blind state"
    }
  },
  "icons": {
    "48": "icons/yellow-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}