Examine source code of RainbowMemo

{
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "RainbowMemo@Sungho.Hwang",
      "strict_min_version": "88.0"
    }
  },
  "name": "RainbowMemo",
  "version": "2.3",
  "description": "Memo pads with rainbow colors.",
  "icons": {
    "32": "rm32.png"
  },
  "browser_action": {
    "default_icon": "rm32.png",
    "default_title": "RainbowMemo"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}