Create jsonnet files to create output files

This allows to create YAML files with rules and JSON files with
dashboard descriptions.

Signed-off-by: beorn7 <beorn@grafana.com>

docs/node-mixin/alerts.jsonnet

@@ -0,0 +1 @@
+std.manifestYamlDoc((import 'mixin.libsonnet').prometheusAlerts)

docs/node-mixin/dashboards.jsonnet

@@ -0,0 +1,6 @@
+local dashboards = (import 'mixin.libsonnet').grafanaDashboards;
+
+{
+  [name]: dashboards[name]
+  for name in std.objectFields(dashboards)
+}

docs/node-mixin/rules.jsonnet

@@ -0,0 +1 @@
+std.manifestYamlDoc((import 'mixin.libsonnet').prometheusRules)