Examine source code of Easy Control

{
  "name": "Easy Control",
  "description": "An extension that allows easy control of various media streaming websites.",
  "version": "4.0.4",
  "manifest_version": 2,
  "minimum_chrome_version": "73",
  "browser_specific_settings": {
    "gecko": {
      "id": "{1bb023b4-c5d0-4e0f-a319-c141ea526900}",
      "strict_min_version": "82.0"
    }
  },
  "icons": {
    "16": "assets/icon16.png",
    "32": "assets/icon32.png",
    "64": "assets/icon64.png",
    "128": "assets/icon128.png"
  },
  "permissions": [
    "clipboardWrite",
    "contextMenus",
    "idle",
    "notifications",
    "storage",
    "tabs",
    "http://*/",
    "https://*/"
  ],
  "web_accessible_resources": [],
  "browser_action": {
    "default_icon": {
      "16": "assets/icon16.png",
      "32": "assets/icon32.png",
      "64": "assets/icon64.png",
      "128": "assets/icon128.png"
    }
  },
  "background": {
    "persistent": false,
    "scripts": [
      "background.bundle.js"
    ]
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true,
    "browser_style": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.bundle.js"
      ]
    }
  ],
  "commands": {
    "1_play_pause": {
      "description": "Plays/Pause"
    },
    "2_next": {
      "description": "Next"
    },
    "3_previous": {
      "description": "Previous"
    },
    "3a_skip_backward": {
      "description": "Skip Backward"
    },
    "3b_skip_forward": {
      "description": "Skip Forward"
    },
    "4_like": {
      "description": "Like"
    },
    "5_unlike": {
      "description": "Unlike"
    },
    "6_dislike": {
      "description": "Dislike"
    },
    "7_undislike": {
      "description": "Undislike"
    },
    "8_volume_up": {
      "description": "Volume Up"
    },
    "9_volume_down": {
      "description": "Volume Down"
    },
    "a_copy_content_link": {
      "description": "Copy current content link"
    }
  }
}