Allow specs to be run with Docker

[dukenguyenxyz]

Description

This PR will allow developers to run clear specs using Docker instead of installing PostgreSQL on their local system. Containerisation will not only help developers test clear without having to install PostgreSQL but also to allow for reproducibility due to the elimination of environmental differences.

In the future, this small change can be upgraded to setting up an entire docker-compose environment so that developers can run clear and clear specs without having to install either PostgreSQL or Crystal, this configuration can also be used for the CI/CD pipeline.

Motivation and Context

How Has This Been Tested?

• All specs passed

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

• [ ] Manual of usage of the new feature.

Checklist:

• [x] My code follows the code style of this project. bin/ameba ran without alert.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.

[dansbits]

Looks like this was proposed a while ago and I don't see any conversation. Any chance running specs in Docker in the future?