update documentation to reflect a better approach

Author: Cerem Cem ASLAN

doc/Ractive/temporary-variables-inside-each-loop.ls

@@ -0,0 +1,13 @@
+# Temporary Variable inside an `each` loop: 
+
+        {{#each myobj}}
+            {{#with (.foo !== 'bar') as tmp}}
+
+                <li>{{.hello}} tmp is: {{tmp}}</li>
+            
+            {{/with}}
+        {{/each}}
+
+`myobj` is not polluted with the `tmp` variables. 
+
+(see https://gitter.im/ractivejs/ractive?at=5f3decae33878e7e602e58d7)