Add a simple index in the docs README. (#669)

Author: MoteHue

docs/README.md

@@ -0,0 +1,45 @@
+# StackHPC Slurm Appliance Documentation
+
+### Operator docs
+
+[Image build](image-build.md)
+
+[CI](ci.md)
+
+[Monitoring and logging](monitoring-and-logging.md)
+
+[Operations guide](operations.md)
+
+[Production deployment](production.md)
+
+[Upgrades](upgrades.md)
+
+[Sequence diagrams](sequence.md)
+
+### Configuration docs
+
+[Alerting](alerting.md)
+
+[Chrony](chrony.md)
+
+[Environments](environments.md)
+
+[K3s](k3s.README.md)
+
+[Networking](networks.md)
+
+[Open OnDemand](openondemand.md)
+
+[Persistent state](persistent-state.md)
+
+#### Experimental fetaures
+
+[Compute init](experimental/compute-init.md)
+
+[Pulp](experimental/pulp.md)
+
+[Slurm controlled rebuild](experimental/slurm-controlled-rebuild.md)
+
+### Contributor docs
+
+[Adding functionality](adding-functionality.md)