Declaring feedgnuplot as a package to pacify the MetaCPAN indexer

Hopefully this is sufficient. We'll see

https://github.com/dkogan/feedgnuplot/pull/16
https://github.com/CPAN-API/metacpan-web/issues/1148
https://github.com/CPAN-API/metacpan-web/issues/1170
https://github.com/CPAN-API/metacpan-web/issues/994