Add instructions for local postgres

[sjwmoveon]

Description

Add additional documentation on how to set up Postgres if using a local installation and not Docker.

Checklist:

• [N/A] I have manually tested my changes on desktop and mobile
• [N/A] The test suite passes locally with my changes
• [N/A] If my change is a UI change, I have attached a screenshot to the description section of this pull request
• My change is 300 lines of code or less, or has a documented reason in the description why it’s longer
• I have made any necessary changes to the documentation
• [N/A] I have added tests that prove my fix is effective or that my feature works
• [N/A] My PR is labeled [WIP] if it is in progress

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[ibrand]

Thanks!