fix: disable networking in singleSiteBlueprint to prevent multisite (#48)

Set networking to false in the single site playground blueprint.
Networking: true can inadvertently enable multisite behaviour.

Closes #39

playground/test.html

@@ -68,7 +68,7 @@
             "landingPage": "/wp-admin/",
             "login": true,
             "features": {
-                "networking": true
+                "networking": false
             },
             "steps": [
                 {