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: sqlc-dev/sqlc#693

Thanks!