Two Github actions to be deployed on repositories for Looker demos

1. Spectacles for validating pull requests using spectacles and notifying of failures / successes in slack
2. Content Validation for validating dashboards in the demo, expoerting LookML dashboards to github and importing LookML dashboards to other instances

Each demo repo needs the following secrets:

• CLIENT_ID: client id for the development instance
• CLIENT_SECRET: client secret for the development instance
• GOOGLEDEMO_CLIENT_ID: client id for the googledemo.looker.com
• GOOGLEDEMO_CLIENT_SECRET: client secret for the googledemo.looker.omc
• PERSONAL_ACCESS_TOKEN: github personal access token

And the following env variables need to be updated in both yaml files:

• DEMO_NAME: Demo name, to be used in slack message (e.g. Ecommerce)
• PROJECT_NAME: LookML project name (e.g. thelook_events)
• HOST: name of the development instance (e.g. demo)