Change Google Calendar Background

{
    "update_url": "https:\/\/clients2.google.com\/service\/update2\/crx",
    "manifest_version": 3,
    "name": "__MSG_name__",
    "version": "1.0.5",
    "default_locale": "en",
    "description": "__MSG_description__",
    "permissions": [
        "storage",
        "tabs"
    ],
    "host_permissions": [
        "*:\/\/chrome-tool.github.io\/*",
        "*:\/\/wallpapers-collection.github.io\/*"
    ],
    "action": {
        "default_icon": "assets\/icons\/icon128.png",
        "default_popup": "popup.html"
    },
    "icons": {
        "16": "assets\/icons\/icon16.png",
        "48": "assets\/icons\/icon48.png",
        "128": "assets\/icons\/icon128.png"
    },
    "content_scripts": [
        {
            "matches": [
                "*:\/\/calendar.google.com\/*"
            ],
            "css": [
                "assets\/css\/style.css"
            ],
            "js": [
                "assets\/js\/loader.js"
            ],
            "run_at": "document_start"
        }
    ],
    "web_accessible_resources": [
        {
            "resources": [
                "assets\/js\/content.js",
                "assets\/js\/utils.js"
            ],
            "matches": [
                "<all_urls>"
            ]
        }
    ]
}