Document genome size limit (#791)

* document size limit

* Update limitations.md

* update

docs/src/content/docs/reference/limitations.md

@@ -0,0 +1,6 @@
+---
+title: Limitations
+description: Current limitations of Loculus
+---
+
+**Genome size**: Loculus currently stores reference genome in Helm values files. The maximum compressed size of the Helm chart is 1 MB. This will create a maximum size for toal reference genomes on the order of 1-10 Megabases (and somewhat dependent on genome complexity).