update to support ruby 3.0

[bruce-ding]

unf_ext-0.0.7.7-x64-mingw32 requires ruby version >= 2.2, < 2.8.dev, which is
incompatible with the current version, ruby 3.0.0p0

[ramereth]

Any update on this? I'm running into this as well.

[johnnyshields]

@knu can we ask your help on this please? Ruby 3.0 looks not supported on x64-mingw32

[Stromweld]

looking at the non mingw32 version the required ruby version is >= 0. Can this gem simply be updated with the same requirement.

[Stromweld]

looks like PR #64 should fix this issue

[johnnyshields]

This is done -- can be closed.