## Is your feature request related to a problem?

You can currently install plugins from Github and NPM sources, but not GitLab

## Describe the solution you'd like

Copy a GitLab URL to install a plugin

## Describe alternatives you've considered

Using the plugin source editor.

## Additional context

Came from a conversation in the Users' slack

#### *Thank you* for your feature request – we love each and every one!

posthog/plugins/utils.py
zip_file = ZipFile(io.BytesIO(archive), "r")
    root_folder = zip_file.namelist()[0]
    file_path = os.path.join(root_folder, filename)
    try:
        with zip_file.open(file_path) as reader:
            return json.loads(reader.read())
    except KeyError:
        return None
def get_json_from_tgz_archive(archive: bytes, filename: str):
    with tarfile.open(fileobj=io.BytesIO(archive), mode="r:gz") as tar:
        if tar.getmembers()[0].isdir():
            root_folder = tar.getmembers()[0].name
        else:
            root_folder = "/".join(tar.getmembers()[0].name.split("/")[0:-1])
        file_path = os.path.join(root_folder, filename)
        extracted_file = tar.extractfile(file_path)
        if not extracted_file:
            return None
        json_bytes = extracted_file.read()
        return json.loads(json_bytes)
def get_json_from_archive(archive: bytes, filename: str):
    try:
        return get_json_from_zip_archive(archive, filename)
    except BadZipFile:
        return get_json_from_tgz_archive(archive, filename)