Describe the bug
I have a user who's on an older version of Safari, and they're getting an error about Intl.ListFormat. Looking through the luxon source, it looks like it's coming from toHuman. Unfortunately, Intl.ListFormat isn't supported by older versions of safari. Here's the error message (manually typed from a screenshot):

TypeError: undefined is not a constructor (evaluating "new Intl.ListFormat(e, t)")

It looks like this was added to luxon fairly recently, here's the place in the source:

To Reproduce
Please share a minimal code example that triggers the problem:
I haven't been able to get a stack trace from our user, but here's where I think it's coming from:

dur.shiftTo('days').toHuman({
    unitDisplay: 'short',
    maximumFractionDigits: 1,
});

Desktop (please complete the following information):

• OS: [OSX]
• Browser [Safari, unknown version, sorry]
• Luxon version [2.3.0]
• Your timezone [America/New_York]

Additional context
CanIUse: https://caniuse.com/?search=intl.listFormat
This is also referenced here by this feature discussion: #688 (comment)