Add mariadb's INSERT ... RETURNING

[Pokerkoffer]

Feature Request

Is your feature request related to a problem? Please describe: Parser does not support INSERT ... RETURNING statement. See https://mariadb.com/kb/en/insertreturning/
Same goes for {REPLACE|DELETE} ... RETURNING

Describe the feature you'd like: See https://mariadb.com/kb/en/insertreturning/

Describe alternatives you've considered: No alternative

Teachability, Documentation, Adoption, Migration Strategy: e.g. INSERT INTO user VALUES('john', 'doe') RETURNING *;

Original request: https://github.com/kyleconroy/sqlc/issues/693

Thanks!