Added tests - restore target es6 - transpile base into es5

src/parser/index.ts

@@ -3,3 +3,4 @@ export { default as PLSQL } from './plsql';
 export { default as HiveSQL } from './hive';
 export { default as FlinkSQL } from './flinksql';
 export { default as SparkSQL } from './spark';
+export { default as PostgresSQL } from './pgsql';

src/parser/pgsql.ts

@@ -4,7 +4,7 @@ import { PostgreSQLParser } from '../lib/pgsql/PostgreSQLParser';
 
 import BasicParser from './common/basicParser';
 
-export default class PLSQLParser extends BasicParser {
+export default class PostgresSQL extends BasicParser {
     public createLexer(input: string): Lexer {
         const chars = new InputStream(input.toUpperCase());
         const lexer = <unknown> new PostgreSQLLexer(chars) as Lexer;