add database to postgresql code example

Example 1: create postgres database

sudo -u postgres psql
postgres=# create database mydb;
postgres=# create user myuser with encrypted password 'mypass';
postgres=# grant all privileges on database mydb to myuser;

Example 2: psql create database

CREATE DATABASE dbname;

Example 3: create database postgres

createdb -h localhost -p 5432 -U postgres testdb
password ******