Examine source code of Save to Medium

{
  "manifest_version": 2,
  "name": "Save to Medium",
  "version": "1.0",
  "description": "Save articles from around the web to your Medium reading list.",
  "homepage_url": "https://medium.com/",
  "externally_connectable": {
    "matches": [
      "*://medium.com/*",
      "*://hatch.dm/*",
      "*://standard.dev/*"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "savetomedium@medium.com",
      "strict_min_version": "42.0"
    }
  },
  "permissions": [
    "http://*/*",
    "https://*/*",
    "storage",
    "tabs",
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "css/toast.css"
      ],
      "js": [
        "init.js"
      ],
      "run_at": "document_end"
    },
    {
      "matches": [
        "*://medium.com/*",
        "*://hatch.dm/*",
        "*://standard.dev/*"
      ],
      "js": [
        "receiveToken.js"
      ],
      "run_at": "document_start"
    }
  ],
  "key": "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAgXujARPMY0j0NicUImPVQJywQBCa1t5hzPo82JP+QnyLGKlMfSEZ+LQea9umbHuPyCJbqksPM4iMP5nZhn0EZITb6o9gTh2U4DUDUQb1Hz15q8HsXzo+u71nysDoTqco4BNOadYCeYV7RmoRZtpeA+sbqhvylD/g7drOfU9hINwAenUMRw5FVPfUMWKoE2AA8SngWu0XdhQkYB8HDfA1bDpJ/fgfs1YT0TCJZaO6Hi7vFvcW5mcVTAru3gTM+WDKe+dL46DVY7UvpmSa5DJkdhYSG+o2RSUAgfRBaxo056qtry4CGNbBpIZlyVWmOWCNvhAGfGwi3QbYTnTaCMvIMQIDAQAB",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_action": {},
  "icons": {
    "16": "images/Medium_Monogram_16px_Light.png",
    "32": "images/Medium_Monogram_32px_Light.png",
    "48": "images/Medium_Monogram_48px.png",
    "128": "images/Medium_Monogram_128px.png"
  },
  "web_accessible_resources": [
    "images/*.png",
    "images/*.svg",
    "fonts/",
    "fonts/*.woff",
    "fonts/*.woff2",
    "css/*.css"
  ]
}