Operator requirements (#283)

Part of stackabletech/documentation#289

Author: razvan

docs/modules/getting_started/pages/index.adoc

@@ -10,9 +10,14 @@ You will need:
 * kubectl
 * optional: Helm
 
+Resource sizing depends on cluster type(s), usage and scope, but as a starting point we recommend a minimum of the following resources for this operator:
+
+* 0.2 cores (e.g. i5 or similar)
+* 256MB RAM
+
 == What's next
 
 The Guide is divided into two steps:
 
 * xref:installation.adoc[Installing the Operators].
-* xref:first_steps.adoc[Setting up the HDFS cluster and verifying it works].
+* xref:first_steps.adoc[Setting up the HDFS cluster and verifying it works].