enhancement suggestion: support for .pkg files

[mnflux]

I am working on two different projects: One uses .sql for PL/SQL packages, the other uses .pkg.

With .sql I can harness all the awesome features of this plugin, but unfortunately .pkg are not supported. So there is no cross package/function/procedure/variable recognition for instance.

Would be really great if .pkg could be added to the supported list.
Thanks for considering and thanks for the awesome language support plugin!