Content script section in manifest fine

manifest.json

/*
Add this to manifest file to inject contentscript.js into web page.
*/
"content_scripts": [
    {
        "matches": [
            "http://*/*",
            "https://*/*"
        ],
        "css": [
            "styles/contentscript.css"
        ],
        "js": [
            "scripts/contentscript.js"
        ],
        "run_at": "document_end",
        "all_frames": false
     }
]