Fix minor typo

Cut and pasting that code gives an error. This is a minor fix, adding a comma at the end of line 64

README.md

@@ -61,7 +61,7 @@ module.exports = {
               noReload: false,
 
               // Try to recover after runtime errors in component init
-              optimistic: false
+              optimistic: false,
 
               // --- Advanced ---