Examine source code of dimmer

{
  "manifest_version": 2,
  "name": "dimmer",
  "version": "3.2.0",
  "description": "A browser extension to dim web pages.",
  "author": "Mehmet Baker",
  "homepage_url": "https://mehmetb.github.io/dimmer",
  "icons": {
    "48": "icons/lightbulb-slash-solid.svg",
    "96": "icons/lightbulb-slash-solid.svg"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "browser_style": true,
    "default_title": "Dim page",
    "default_popup": "/popup/popup.html",
    "theme_icons": [
      {
        "light": "icons/browser-action-light.svg",
        "dark": "icons/browser-action-dark.svg",
        "size": 16
      },
      {
        "light": "icons/browser-action-light.svg",
        "dark": "icons/browser-action-dark.svg",
        "size": 32
      }
    ]
  },
  "commands": {
    "Toggle Dim (All tabs)": {
      "suggested_key": {
        "default": "Ctrl+Alt+N"
      }
    },
    "Toggle Dim (Active tab only)": {
      "suggested_key": {
        "default": "Ctrl+Alt+B"
      }
    }
  },
  "content_scripts": [
    {
      "js": [
        "content_scripts/overlay.js"
      ],
      "matches": [
        "<all_urls>"
      ],
      "match_about_blank": true,
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{48be9eda-8d28-4a3c-8c1c-cd6161dbf076}"
    }
  }
}