add a flag on to the sls object to let it know SFE is enabled

this is different from the plugin just being loaded and necessary for SFO to
determine if it needs to check the version of the plugin and issue a warning.
could all be done in the plugin, but if we ever want to move to auto-update,
the framework hsa to drive the actions

src/lib/plugin.js

@@ -83,6 +83,8 @@ class ServerlessEnterprisePlugin {
       return
     }
 
+    sls.enterpriseEnabled = true
+
     // Defaults
     this.sls = sls
     this.state = {} // Useful for storing data across hooks