contributing: clarify "running website locally"

contributing: clarify "running website locally" section
another step is required to start the local webserver

CONTRIBUTING.md

@@ -100,17 +100,16 @@ Open [http://localhost:8080/monaco-editor/test/?editor=src&monaco-typescript=src
 # create a local release
 /src/monaco-editor> npm run release
 
-# open http://localhost:8080/monaco-editor/website/
-
 # build the website
 /src/monaco-editor> npm run build-website
 
+# start local webserver
+/src/monaco-editor> npm run simpleserver
+
 # open http://localhost:8080/monaco-editor-website/
 
 ```
 
----
-
 ## Shipping a new monaco-editor npm module
 
 #### 1. Ship a new `monaco-editor-core` npm module