Support for PgHasArrayType for PgUxx structs

[ronnybremer]

When trying to use the PgU32 and similar structs from this crate for array columns, the rust compiler errors out with trait PgHasArrayType missing. According to this documentation of SqlX PgHasArrayType do you think it could be added for the structs of this crate?

[bitfl0wer]

This looks to be doable. I will add it to my roadmap! :) Thank you for requesting this.