{{alias}}( [p] )
    Returns a directory for user-specific configuration files.

    On Windows platforms, the function first checks for a `LOCALAPPDATA`
    environment variable before checking for an `APPDATA` environment variable.
    This means that machine specific user configuration files have precedence
    over roaming user configuration files.

    On non-Windows platforms, if the function is unable to locate the current
    user's `home` directory, the function returns `null`. Similarly, on Windows
    platforms, if the function is unable to locate an application data
    directory, the function also returns `null`.

    Parameters
    ----------
    p: string (optional)
        Path to append to a base directory.

    Returns
    -------
    out: string|null
        Directory.

    Examples
    --------
    > var dir = {{alias}}()
    e.g., '/Users/<username>/Library/Preferences'
    > dir = {{alias}}( 'appname/config' )
    e.g., '/Users/<username>/Library/Preferences/appname/config'

    See Also
    --------