PostgreSQL xml type

[lsk569937453]

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when the postgreSQL of sqlx not support xml type.

Describe the solution you'd like
I want the postgreSQL of sqlx support xml type.The type is https://www.postgresql.org/docs/current/datatype-xml.html.