Examine source code of GameKeyMove

{
  "name": "GameKeyMove",
  "description": "Like Game Moveing, you control page using only left hand on keyboard. USAGE:  [W][S]key to scroll up/down ,  move history: [A][D]key,  move tab: [Q][E] key,  zoomIn/Out:[1][2],  reload:[R], duplicate tab[B], create new tab [N], close tab[C]. And [ESC] or tool bar button toggle this mode on/off. Initial state is off. and also this state sync browser & each tab page equal with a little lag.  This addon don't work at TextArea and Input as far. Of cource, at addon or new tab page neither.<br><br>contribute(icon):<br> color<br> <div>Icons made by <a href='https://www.flaticon.com/authors/prosymbols' title='Prosymbols'>Prosymbols</a> from <a href='https://www.flaticon.com/' title='Flaticon'>www.flaticon.com</a> is licensed by <a href='http://creativecommons.org/licenses/by/3.0/' title='Creative Commons BY 3.0' target='_blank'>CC 3.0 BY</a></div><br><br>mono<br><div>Icons made by <a href='http://www.freepik.com' title='Freepik'>Freepik</a> from <a href='https://www.flaticon.com/' title='Flaticon'>www.flaticon.com</a> is licensed by <a href='http://creativecommons.org/licenses/by/3.0/' title='Creative Commons BY 3.0' target='_blank'>CC 3.0 BY</a></div>",
  "manifest_version": 2,
  "version": "1.0.2resigned1",
  "icons": {
    "64": "icons/002-keyboard.png"
  },
  "browser_action": {
    "default_icon": {
      "64": "icons/001-keyboard-1.png"
    }
  },
  "content_scripts": [
    {
      "all_frames": true,
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "contentScript.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "<all_urls>",
    "activeTab",
    "tabs",
    "webNavigation"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{e00f846c-c035-42bd-b27e-bcd16ea0be6e}"
    }
  }
}