Babel parser should parse PostgreSQL's SET, RESET, BEGIN, SHOW, ROLLBACK, COMMIT commands

Babel parser can not parse BEGIN [1], SHOW [2], ROLLBACK [3], COMMIT [4] commands at the moment.

It can parse SET [5] and RESET [6], but not completely. For instance, it can not parse the following statement:

SET SCHEMA public,public,"$user"

The syntax for these commands is as follows:

• BEGIN [1]:

  BEGIN [ WORK | TRANSACTION ] [ transaction_mode [, ...] ] 
  
  where transaction_mode is one of: ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED } READ WRITE | READ ONLY [ NOT ] DEFERRABLE
  

• SHOW [2]:

  SHOW (<TRANSACTION ISOLATION LEVEL> | <string literal>)
  

• ROLLBACK [3]:

  ROLLBACK [ WORK | TRANSACTION ] [ AND [ NO ] CHAIN ]
  

• COMMIT [4]:

  COMMIT [ WORK | TRANSACTION ] [ AND [ NO ] CHAIN ]
  

• SET [5]

  SET [ SESSION | LOCAL ] configuration_parameter { TO | = } { value | 'value' | DEFAULT }
  SET [ SESSION | LOCAL ] TIME ZONE { value | 'value' | LOCAL | DEFAULT }
  SET [ SESSION | LOCAL ]  { SCHEMA | SEED | NAMES } value
  
  Values can be specified as string constants, identifiers, numbers, or comma-separated lists of these
  

• RESET [6]

  RESET <parameter>;
  

[1] https://www.postgresql.org/docs/current/sql-begin.html
[2] https://www.postgresql.org/docs/current/sql-show.html
[3] https://www.postgresql.org/docs/current/sql-rollback.html
[4] https://www.postgresql.org/docs/current/sql-commit.html
[5] https://www.postgresql.org/docs/current/sql-set.html
[6] https://www.postgresql.org/docs/current/sql-reset.html