Specify the behaviour of the ScrollTimeline Constructor. Fixes issue #6 and issue #7.

Author: theres-waldo

Overview.bs

@@ -370,6 +370,14 @@ not by wall-clock time, but by the progress of scrolling in a [=scroll container
 
 <div link-for-hint="ScrollTimeline">
 
+<div class="constructors">
+
+:   <dfn constructor for=ScrollTimeline lt="ScrollTimeline(options)">ScrollTimeline(options)</dfn>
+::  Creates a new {{ScrollTimeline}} object. The attributes of the {{ScrollTimeline}} are 
+    initialized with the respective members of the {{options}} dictionary.
+
+</div>
+
 <div class="attributes">
 
 :   <dfn attribute for=ScrollTimeline>scrollSource</dfn>