Specs: Clarify currentScript behaviour

sky/specs/apis.md

 APIs
 ====
 
 The Sky core API
 ----------------
 
 ```javascript
 module 'sky:core' {
 
   // EVENTS
@@ skipping 156 matching lines @@
   interface IframeElement : Element { }
   interface TElement : Element { }
   interface AElement : Element { }
   interface TitleElement : Element { }
 
 
 
   // MODULES
   abstract interface AbstractModule : EventTarget {
     Promise<any> import(String url); // O(Yikes) // returns the module's exports
-    ScriptElement? currentScript; // O(1) // returns the <script> element currently being executed if any, else null
+    ScriptElement? currentScript; // O(1) // returns the <script> element currently being executed if any, and if it's in this module; else null
   }
 
   interface Module : AbstractModule {
     constructor (Application application, Document document); // O(1)
     attribute any exports; // O(1) // defaults to the module's document
     readonly attribute Document document; // O(1) // the module's document
     readonly attribute Application application; // O(1)
   }
 
   interface Application : AbstractModule {
@@ skipping 161 matching lines @@
   the core mojo fabric JS API   sky:mojo:fabric:core
   the asyncWait/cancelWait mojo fabric JS API (interface to IPC thread)  sky:mojo:fabric:ipc
   the mojom for the shell, proxying through C++ so that the shell pipe isn't exposed  sky:mojo:shell
   the sky API  sky:core
   the sky debug symbols for private APIs  sky:debug
 ```
 
 TODO(ianh): determine if we want to separate the "this" from the
 Document, especially for Modules, so that exposing a module's element
 doesn't expose the module's exports attribute.