Chore: Hugo upgrade (#17494)

* Fix: Upgrade hugo wip

* Chore: Rename index to _index for latest hugo

* Chore: Use relative refs, no starting slash

* Feat: Add possibility to mount layouts from grafana.org project

docs/sources/features/datasources/_index.md

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+title = "Data Sources"
+type = "docs"
+aliases = ["/datasources/overview/"]
+[menu.docs]
+name = "Data Sources"
+identifier = "datasources"
+parent = "features"
+weight = 5
++++
+
+# Data Source Overview
+
+Grafana supports many different storage backends for your time series data (Data Source). Each Data Source has a specific Query Editor that is customized for the features and capabilities that the particular Data Source exposes.
+
+## Querying
+
+The query language and capabilities of each Data Source are obviously very different. You can combine data from multiple Data Sources onto a single Dashboard, but each Panel is tied to a specific Data Source that belongs to a particular Organization.
+
+## Supported Data Sources
+
+The following datasources are officially supported:
+
+* [Graphite]({{< relref "graphite.md" >}})
+* [Prometheus]({{< relref "prometheus.md" >}})
+* [InfluxDB]({{< relref "influxdb.md" >}})
+* [Elasticsearch]({{< relref "elasticsearch.md" >}})
+* [Google Stackdriver]({{< relref "stackdriver.md" >}})
+* [AWS CloudWatch]({{< relref "cloudwatch.md" >}})
+* [Azure Monitor]({{< relref "azuremonitor.md" >}})
+* [Loki]({{< relref "loki.md" >}})
+* [MySQL]({{< relref "mysql.md" >}})
+* [PostgreSQL]({{< relref "postgres.md" >}})
+* [Microsoft SQL Server (MSSQL)]({{< relref "mssql.md" >}})
+* [OpenTSDB]({{< relref "opentsdb.md" >}})
+* [Testdata]({{< relref "testdata.md" >}})
+
+## Data source plugins
+
+Since grafana 3.0 you can install data sources as plugins. Checkout [Grafana.net](https://grafana.com/plugins) for more data sources.