Add GitHub schema to Postgres

[JerryHue]

Issue This PR Addresses

Fixes #3215

Type of Change

• Bugfix: Change which fixes an issue
• New Feature: Change which adds functionality
• Documentation Update: Change which improves documentation
• UI: Change which improves UI

Description

This PR adds a new table schema to Postgres to store the GitHub data we will scrape from the posts.

Steps to test the PR

1. Pull the changes.
2. Start the services (pnpm run services:start).
3. Go to localhost:8910.
4. Head over the default project and then find the database tables. There should be tables named github_users, github_repositories, and github_issues.

Checklist

• Quality: This PR builds and passes our npm test and works locally
• Tests: This PR includes thorough tests or an explanation of why it does not
• Screenshots: This PR includes screenshots or GIFs of the changes made or an explanation of why it does not (if applicable)
• Documentation: This PR includes updated/added documentation to user exposed functionality or configuration variables are added/changed or an explanation of why it does not(if applicable)

[gitpod-io]