Examine source code of Backspace Enabler

{
  "manifest_version": 2,
  "name": "Backspace Enabler",
  "author": "Mikko Hämäläinen",
  "version": "1.0",
  "description": "Return backspace functionality to Firefox",
  "homepage_url": "https://extensionworkshop.com",
  "permissions": [
    "activeTab",
    "tabs",
    "storage"
  ],
  "page_action": {
    "default_icon": {
      "16": "data/icons/16.png",
      "32": "data/icons/32.png",
      "48": "data/icons/48.png",
      "64": "data/icons/64.png"
    },
    "default_title": "enable-backspace"
  },
  "browser_action": {
    "default_icon": "data/icons/32.png",
    "default_title": "enable-backspace"
  },
  "icons": {
    "16": "data/icons/16.png",
    "32": "data/icons/32.png",
    "48": "data/icons/48.png",
    "64": "data/icons/64.png",
    "128": "data/icons/128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "all_frames": false,
      "js": [
        "data/content_script/inject.js"
      ],
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{f6cad17e-f1e1-4512-ab72-adb4e12e9daa}"
    }
  }
}