PostgreSQL "DO" statement support

[Knyntsje]

Describe the bug
The PostgreSQL "DO" statement is not supported: https://www.postgresql.org/docs/current/sql-do.html.
Parsing the SQL below gives the following error: Expected "#", "--", "/*", ":=", "=", or [ \\t\\n\\r] but "$" found.

Database Engine
PostgreSQL

To Reproduce
Reproduction code (https://playcode.io/empty-typescript-playground--019ac65c-53cf-741c-a307-87d71bda1d4b):

import { Parser } from "node-sql-parser/build/postgresql";

const parser = new Parser();
const ast = parser.astify(`
    DO $$
    DECLARE
        test INTEGER;
    BEGIN
        SELECT 1 INTO test;
    END
    $$;
`);

console.log(ast);

node-sql-parser version: 5.3.13
node version: 25.2.1

Expected behavior
Support for "DO" statements.