build-all.

    Takes an optional LANG argument with the name of the language to serve, by default
    en.
    """
    # Enable line numbers during local development to make it easier to highlight
    os.environ["LINENUMS"] = "true"
    if lang is None:
        lang = "en"
    lang_path: Path = docs_path / lang
    os.chdir(lang_path)
    mkdocs.commands.serve.serve(dev_addr="127.0.0.1:8008")