Examine source code of Custom Sourcemaps

{
  "manifest_version": 2,
  "version": "0.2.1",
  "name": "__MSG_extensionName__",
  "description": "__MSG_extensionDescription__",
  "devtools_page": "devtools/page.html",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "<all_urls>",
    "webRequest",
    "webRequestBlocking",
    "storage",
    "unlimitedStorage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{3355cdc2-54ec-4df2-9239-ea94d0832336}"
    }
  },
  "default_locale": "en_US"
}