Update changelog?

[mperham]

There are undocumented versions not in the changelog. If you want a native English speaker, I would be glad to volunteer.

[hsbt]

Thanks for your friendly support. Maintaining CHANGELOG is:

• Easily conflict pull-request like Add support for symbols in #shift_age #73
• It makes release work hard. Because gh releases can't work before git tag. It's not useful with rake release with bundler task.

I would like to switch https://github.com/ruby/logger/releases/ from CHANGELOG.

[mperham]

I understand, thanks.