Add instructions to quick-start to set up database permissions

[mcapodici]

Describe the bug
The steps on https://docs.nextacular.co/getting-started/quick-start are not completely clear.

To Reproduce
Steps to reproduce the behavior:

1. Look at the steps above
2. There is no indication of how to set up your developer DB
3. If you forget to ALTER USER nextacular CREATEDB; it seems to come up with error:

Error: P3014

Prisma Migrate could not create the shadow database. Please make sure the database user has permission to create databases. Read more about the shadow database (and workarounds) at https://pris.ly/d/migrate-shadow

Expected behavior
Instructions on how to create the Postgres DB. E.g.

CREATE USER nextacular WITH PASSWORD 'nextacular';
CREATE DATABASE nextaculardb WITH OWNER = 'nextacular';
GRANT ALL PRIVILEGES ON DATABASE nextaculardb TO nextacular;
ALTER USER nextacular CREATEDB;

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: Windows 11
• Browser: N/A
• Version: N/A