Examine source code of DosparaPlusTax

{
  "manifest_version": 2,
  "name": "DosparaPlusTex",
  "version": "1.2resigned1",
  "description": "Display tex added price on Dospara web page.",
  "icons": {
    "48": "icons/dos.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://used.dospara.co.jp/sale/*"
      ],
      "js": [
        "dostax.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{5a3dfdf5-260e-42a7-91dc-0946a526e8a5}"
    }
  }
}