Examine source code of Download Blocker

{
  "manifest_version": 2,
  "name": "Download Blocker",
  "version": "1.4",
  "description": "Disable downloading files to disk",
  "applications": {
    "gecko": {
      "strict_min_version": "60.0",
      "id": "download-blocker@clear-code.com"
    }
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}