Examine source code of VolMax - Volume Booster & EQ

{
  "manifest_version": 3,
  "name": "VolMax - Volume Booster & EQ",
  "version": "1.7.1",
  "description": "Boost volume up to 1000%, 6-band EQ, balance, night mode, per-tab memory, and hotkeys.",
  "browser_specific_settings": {
    "gecko": {
      "id": "volmax@oplpet95.gmail.com",
      "strict_min_version": "109.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "activeTab",
    "scripting",
    "storage",
    "tabs"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "injected.js"
      ],
      "run_at": "document_start",
      "all_frames": true,
      "world": "MAIN"
    },
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle",
      "all_frames": true
    },
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "favicon.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "background": {
    "service_worker": "background.js",
    "scripts": [
      "constants.js",
      "background.js"
    ]
  },
  "commands": {
    "volume-up": {
      "suggested_key": {
        "default": "Alt+Shift+Up"
      },
      "description": "Increase volume by 10%"
    },
    "volume-down": {
      "suggested_key": {
        "default": "Alt+Shift+Down"
      },
      "description": "Decrease volume by 10%"
    },
    "volume-mute": {
      "suggested_key": {
        "default": "Alt+Shift+M"
      },
      "description": "Toggle mute"
    }
  }
}