Examine source code of Clock

{
    "manifest_version": 2,
    "name": "__MSG_extensionName__",
    "version": "0.4.3",

    "description": "__MSG_extensionName__",
    "default_locale":"en",

    "browser_action":{
        "default_title":"clock",
        "browser_style":true,
        "default_popup":"popup/popup.html"
    },
    
    "icons": {
        "48": "clock.png"
    },

    "content_scripts":[
        {
        "matches":["<all_urls>"],
        "js":["js/lego_cale.js", "lib/react-16.13.1.umd.min.js", "lib/react-dom-16.13.1.umd.min.js", "js/utils.js", "js/widgets.js", "js/clock.js", "js/alert.js"]
        // "js":["js/lego_cale.js", "dev_lib/react.development.js", "dev_lib/react-dom.development.js", "js/utils.js", "js/widgets.js", "js/clock.js", "js/alert.js"]
        }
    ],

    "background":{
        "scripts":["js/font.js", "js/utils.js", "js/background.js"]
    },

    "options_ui": {
        "page": "options/options.html",
        "open_in_tab": true
    },

    "permissions":[
        "storage",
        "tabs",
        "activeTab"
    ]
}