Examine source code of Text Blaster Pro

{
  "manifest_version": 2,
  "name": "Text Blaster Pro",
  "description": "SMS Blaster for Android and iOS. Send mass text messages directly from your own phone.",
  "version": "1.1.11",
  "icons": {
    "16": "icon/16-light.png",
    "32": "icon/32-light.png",
    "48": "icon/48-light.png",
    "128": "icon/128-light.png"
  },
  "permissions": [
    "storage",
    "tabs",
    "alarms"
  ],
  "web_accessible_resources": [
    "/extension-installed.js",
    "/icon/favicon.ico",
    "/whatsapp-search-contact.js",
    "content-scripts/sbm-android-refactored.css",
    "content-scripts/sbm-android.css",
    "content-scripts/sbm-textnow.css",
    "content-scripts/sbm-whatsapp.css"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "admin@textblaster.pro",
      "strict_min_version": "109.0"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Default Popup Title",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://messages.google.com/*, https://web.whatsapp.com/*"
      ],
      "run_at": "document_start",
      "js": [
        "content-scripts/sbm-always-visible.js"
      ],
      "world": "MAIN"
    },
    {
      "matches": [
        "https://messages.google.com/*"
      ],
      "run_at": "document_end",
      "js": [
        "content-scripts/sbm-android-refactored.js",
        "content-scripts/sbm-android.js"
      ]
    },
    {
      "matches": [
        "http://localhost/*",
        "https://*.app.textblaster.pro/*"
      ],
      "run_at": "document_end",
      "js": [
        "content-scripts/sbm-api.js"
      ]
    },
    {
      "matches": [
        "https://www.textnow.com/*"
      ],
      "run_at": "document_end",
      "js": [
        "content-scripts/sbm-textnow.js"
      ]
    },
    {
      "matches": [
        "https://web.whatsapp.com/*"
      ],
      "run_at": "document_end",
      "js": [
        "content-scripts/sbm-whatsapp.js"
      ]
    }
  ]
}