Examine source code of OneSpace

{
  "manifest_version": 2,
  "name": "OneSpace",
  "version": "0.0.4",
  "description": "No more double spaces after periods! With OneSpace, every site you visit will show only one space after end punctuation.",
  "author": "Mike Boyle",
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*",
        "file:///*"
      ],
      "js": [
        "noDoubleSpace.js"
      ],
      "run_at": "document_end",
      "all_frames": true
    }
  ]
}