fix(parameter-rendering): improve punctuation and spacing (#4145)

src/core/components/parameter-row.jsx

@@ -158,7 +158,7 @@ export default class ParameterRow extends Component {
             <Markdown source={
                 "<i>Available values</i>: " + paramItemsEnum.map(function(item) {
                     return item
-                  }).toArray()}/> 
+                  }).toArray().join(", ")}/> 
             : null
           }