chore(env): Adding required env inside chaosengine (#479)

Signed-off-by: shubhamchaudhary <shubham@chaosnative.com>

charts/generic/node-cpu-hog/engine.yaml

@@ -21,6 +21,10 @@ spec:
             - name: NODE_CPU_CORE
               value: ''
             
-            # ENTER THE COMMA SEPARATED TARGET NODES NAME
+            ## percentage of total nodes to target
+            - name: NODES_AFFECTED_PERC
+              value: ''
+
+            # provide the comma separated target node names
             - name: TARGET_NODES
               value: ''