Examine source code of Subreddit Blocker

{
  "manifest_version": 3,
  "name": "Subreddit Blocker",
  "version": "1.3.5",
  "action": {
    "default_popup": "index.html",
    "default_title": "Subreddit Blocker"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "subredditblocker@gmail.com"
    }
  },
  "icons": {
    "16": "icon16.png",
    "32": "icon32.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "default_locale": "en",
  "description": "Block subreddits from feeds such as /r/all and /r/popular",
  "author": "Shea Meyers",
  "permissions": [
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://www.reddit.com/",
        "https://www.reddit.com/?*",
        "https://www.reddit.com/r/all/",
        "https://www.reddit.com/r/all/?*",
        "https://www.reddit.com/r/popular/",
        "https://www.reddit.com/r/popular/?*",
        "https://old.reddit.com/",
        "https://old.reddit.com/?*",
        "https://old.reddit.com/r/all/",
        "https://old.reddit.com/r/all/?*",
        "https://old.reddit.com/r/popular/",
        "https://old.reddit.com/r/popular/?*"
      ],
      "js": [
        "block-subreddit-cards.js"
      ]
    }
  ]
}