add changelog file

It is a good practice to include a changelog within you CPAN distribution. There is even a [special website](http://changes.cpanhq.org/) which monitors whether all CPAN uploads conform to a [standard Changes format](http://metacpan.org/module/CPAN::Changes::Spec). You can look at our (completed) [quest](https://questhub.io/realm/perl/quest/51f0337718ba7d3959000086) for further details.

There are multiple `Dist::Zilla` plugins to manage `Changes` file (e.g. [this one](https://metacpan.org/pod/Dist::Zilla::Plugin::NextRelease)).

Cheers!