Add CI Workflow Automation (Deploy & Test)

[luffyofproduct]

Summary:

This PR adds functionality to automatically validate proposed changes in an isolated pre-Production environment (CI).

Details:

• Added a new ci target in a project profiles.yml
• Added a GitHub Actions workflow file for:
  • ci.yml - Automatically deploy & test model changes in a ci environment
• Created repository Secrets to securely store credentials
• Using env_vars to set key dbt information at runtime (populated w/ Secrets)

Links:

• GitHub Actions Docs
• Using Secrets in GitHub Actions
• dbt_profiles_dir
• dbt env_var
• dbt State