Starter Kit: CI/CD with Github Actions

### Background on the problem the feature will solve/improved user experience
Manual cloud deployments are tedious.

### Describe the solution you'd like
Once we've validated our manual deployments we would like to have CI/CD to deploy easily to cloud across all Open Sentencing repositories.

### Tasks

Add github actions for:
- [ ] building
- [ ] unit testing
- [ ] accessibility testing
- [ ] linting
- [ ] deployment

Related Issues:
- https://github.com/Call-for-Code-for-Racial-Justice/Open-Sentencing-Aggregator/issues/30
- https://github.com/Call-for-Code-for-Racial-Justice/Open-Sentencing-Aggregator/pull/20
- https://github.com/Call-for-Code-for-Racial-Justice/Open-Sentencing/issues/28
- https://github.com/Call-for-Code-for-Racial-Justice/Open-Sentencing-Aggregator/issues/28
- https://github.com/Call-for-Code-for-Racial-Justice/Open-Sentencing-UI/issues/63

### Acceptance Criteria

Commencez par examiner les issues et la pull request associées, en particulier Aggregator issue 30 et PR 20, afin de comprendre le processus manuel de deployment existant entre les repositories. L’issue ne nomme aucun fichier, test, fournisseur cloud ni critère d’acceptation ; sa réalisation devrait couvrir des workflows pour le build, les unit tests, les accessibility tests, le linting et le deployment.

Rédigé par le modèle d'indexation à partir du texte de l'issue.