[
    {
        "name": "Some Blocks",
        "extensionURL": "static/extensions/example-extension.js",
        "md5": "76f99773dd4eb59f86cd11bba6ad3cb9.svg"
    }
]

[
    {
        "name": "Some Blocks",
        "extensionURL": "static/extensions/example-extension.js",
        "md5": "76f99773dd4eb59f86cd11bba6ad3cb9.svg"
    },
    {
        "name": "Pen",
        "extensionURL": "",
        "md5": "76f99773dd4eb59f86cd11bba6ad3cb9.svg"
    }
]

Add pen extension to library
Add pen extension to library
