add support for surrealdb

[ralyodio]

add support for surrealdb

[neilotoole]

@ralyodio: As currently architectured, the backend DB drivers that sq supports must implement the Go stdlib database/sql interface. From a quick read of the surrealdb Go driver docs, it seems that surrealdb uses a custom driver.

Ultimately, sq could be refactored to support non-database/sql, but it may be an easier lift to wrap the custom surrealdb drivers with a database/sql driver.

To be clear: I would be very, very happy to add support for surrealdb.