Psql commands

RisingWave supports the following psql commands:

Command	Description
\d	Lists all relations in the current database. Sources are not yet supported.
\di	Lists all indexes in the current database.
\dm	Lists all materialized views in the current database.
\dt	Lists all tables in the current database.
\du	Lists all users and their privileges in the current database.
\q	Quits psql.