docs: add scaleout article to index

Signed-off-by: mbshields <mshields@alum.mit.edu>

mkdocs.yml

@@ -126,6 +126,7 @@ nav:
     - Retention Policies: articles/retention.md
     - Mirroring: articles/mirroring.md
     - Clustering: articles/clustering.md
+    - Easy scaling of a cluster: articles/scaleout.md
     - Monitoring: articles/monitoring.md
     - Using GraphQL for Enhanced Searches: articles/graphql.md
     - Benchmarking with zb: articles/benchmarking-with-zb.md