Examine source code of Snapsize

{
  "manifest_version" : 3 ,
  "name" : "Snapsize",
  "version" : "2.0.0",
  "description" : "Resize the window to exact device and breakpoint sizes in one click. Sweep through breakpoints, compare sizes side by side, and save screenshots at each size.",
  "author": "Dennis Bierreth Fernandez",
  "homepage_url" : "https://dennisbf.design",
  "icons" : {
    "48" : "icons/icon.svg",
    "96" : "icons/icon.svg"
  },
  "permissions" : [
    "storage" ,
    "activeTab" ,
    "downloads" ,
    "scripting" 
  ],
  "action" : {
    "default_title" : "Snapsize (Alt+Shift+R)",
    "default_popup" : "popup/popup.html",
    "default_icon" : "icons/icon.svg"
  },
  "options_ui" : {
    "page": "options/options.html" ,
    "open_in_tab": true
  },
  "background" : {
    "scripts" : [
      "shared/presets.js" ,
      "background.js" 
    ]
  },
  "commands" : {
    "_execute_action": {
      "suggested_key": {
        "default": "Alt+Shift+R"
      },
      "description" : "Open Snapsize"
    },
    "preset-1": {
      "suggested_key": {
        "default": "Alt+Shift+1"
      },
      "description" : "Resize to favourite preset 1"
    },
    "preset-2": {
      "suggested_key": {
        "default": "Alt+Shift+2"
      },
      "description" : "Resize to favourite preset 2"
    },
    "preset-3": {
      "suggested_key": {
        "default": "Alt+Shift+3"
      },
      "description" : "Resize to favourite preset 3"
    },
    "preset-4": {
      "suggested_key": {
        "default": "Alt+Shift+4"
      },
      "description" : "Resize to favourite preset 4"
    },
    "restore": {
      "suggested_key": {
        "default": "Alt+Shift+0"
      },
      "description" : "Restore the window to its original size"
    },
    "screenshot": {
      "suggested_key": {
        "default": "Alt+Shift+P"
      },
      "description" : "Save a screenshot at the current size"
    },
    "site-size": {
      "suggested_key": {
        "default": "Alt+Shift+L"
      },
      "description" : "Apply the size remembered for this site"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "snapsize@dennisbf.design",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "optional_permissions" : [
    "tabs" 
  ]
}