Examine source code of Immich Photos for Proton Mail

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 3,
  "name": "Immich Photos for Proton Mail",
  "short_name": "Immich for Proton",
  "version": "0.1.4",
  "description": "Attach photos from your self-hosted Immich library directly into Proton Mail compose windows.",
  "homepage_url": "https://github.com/kaishi00/immich-photos-for-proton",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png",
    "128": "icons/icon-128.png",
    "512": "icons/icon-512.png"
  },
  "background": {
    "service_worker": "background.js"
  },
  "content_scripts": [
    {
      "matches": [
        "https://mail.proton.me/*"
      ],
      "js": [
        "content/content.js"
      ],
      "css": [
        "content/content.css"
      ],
      "run_at": "document_idle"
    }
  ],
  "host_permissions": [
    "https://mail.proton.me/*"
  ],
  "optional_host_permissions": [
    "https://*/*"
  ],
  "permissions": [
    "storage"
  ],
  "options_ui": {
    "page": "options/options.html",
    "open_in_tab": true
  },
  "action": {
    "default_title": "Immich Photos for Proton Mail",
    "default_icon": {
      "48": "icons/icon-48.png",
      "96": "icons/icon-96.png"
    },
    "default_popup": "options/options.html"
  },
  "web_accessible_resources": [
    {
      "resources": [
        "picker/picker.html",
        "picker/picker.js",
        "picker/picker.css",
        "picker/suppress-resize-observer.js"
      ],
      "matches": [
        "https://mail.proton.me/*"
      ]
    }
  ]
}