Make sure data sources are working on play.grafana.org

Ensure we have a working data source and some test dashboards connected to the [grafana play instance](https://play.grafana.org/). --- | Name | Has working datasource | Has demo dashboards | Notes | |------|-----------|---------------------|-------| | BigQuery | ✅ true | [true](https://play.grafana.org/dashboards/f/demo-bigquery/demo-bigquery) | some demo dashboards have errors | | Postgres | ❌ false | false | | | MySQL | ✅ true (has 2) | [true](https://play.grafana.org/dashboards/f/demo-mysql/demo-mysql-8) (dashboards are bad) | | | GitHub | ✅ true | [true](https://play.grafana.org/dashboards/f/bb613d16-7ee5-4cf4-89ac-60dd9405fdd7/demo-github) (dashboards are bad) | | | GoogleSheets | ✅ true (has 2) | false | | | Zabbix | ❌ false | false | | | Infinity | ✅ true (has 3) | [true](https://play.grafana.org/dashboards/f/demo-infinity/demo3a-infinity-json-csv-and-more) (could be better) | |