isMobilePhone locale should default to 'any'

[towc]

currently, if you don't pass a second argument, it fails with invalid locale 'undefined', which means you have to look at the docs/source code to figure out what to do, while it's very likely you just want any locale.

setting the default locale to any shouldn't break any code, because if there's no second argument, it just fails.

Agree or disagree?

[chriso]

Agreed. Happy to accept a PR with the change.

[towc]

1 PR and a soda coming up

[chriso]

Fixed by #874. This will go out in the next release.