Examine source code of GarminGraphs

{
  "manifest_version": 2,
  "name": "GarminGraphs",
  "version": "1.3.1",
  "description": "Adds Colored Zones to Garmin Activity Graphs",
  "icons": {
    "48": "images/icon48.png"
  },
  "permissions": [
    "storage",
    "webRequest",
    "webNavigation",
    "webRequestBlocking",
    "https://connect.garmin.com/modern/proxy/activity-service/activity/*",
    "https://connect.garmin.com/modern/proxy/biometric-service/heartRateZones/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://connect.garmin.com/*"
      ],
      "js": [
        "libs/d3-array.v2.min.js",
        "libs/d3-axis.v2.min.js",
        "libs/d3-format.v2.min.js",
        "libs/d3-interpolate.v2.min.js",
        "libs/d3-path.v2.min.js",
        "libs/d3-scale.v3.min.js",
        "libs/d3-selection.v2.min.js",
        "libs/d3-shape.v2.min.js",
        "scripts/content.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "scripts/background.js"
    ]
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{93714d9d-3af9-4e4d-941d-1072bc3f5614}"
    }
  }
}