Examine source code of Jira Mood

{
  "manifest_version": 2,
  "name": "Jira Mood",
  "version": "1.2",
  "description": "Mood for Jira Board, only work on 'assignee='.",
  "permissions": [
    "storage"
  ],
  "applications": {
    "gecko": {
      "id": "@jira-mood"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/secure/RapidBoard.jspa*",
        "*://*/*/secure/RapidBoard.jspa*",
        "*://*/*/*/secure/RapidBoard.jspa*"
      ],
      "js": [
        "mood.js"
      ],
      "css": [
        "mood.css"
      ]
    }
  ]
}