Convert to `typing.NamedTuple`

[nstarman]

https://github.com/glass-dev/glass/blob/c9a816dbbee8bccf8f9da5430fbb59e104c62f6d/glass/shells.py#L80

class RadialWindow(NamedTuple):
    """Docstring."""

    attr1: float
    """Description."""

    attr2: float
    """Description."""

[ntessore]

Good catch. I was thinking whether a dataclass might not be better, but there probably are still a few cases of for za, wa, zeff in radial_windows scattered around.