Specs: Split apis.md into dom.md, events.md, idl.md, and move the remainder into README.md and modu…

sky/specs/animation.md

+Animation API
+=============
+
+```javascript
+
+dictionary EasingFunctionSettings {
+  Float duration; // required
+  Callback? completionCallback = null;
+}
+
+abstract class EasingFunction {
+  abstract constructor (EasingFunctionSettings settings);
+  abstract Float getFactor(Float time);
+    // calls completionCallback if time >= duration
+    // then returns a number ostensibly in the range 0.0 to 1.0
+    // (but it could in practice go outside this range, e.g. for
+    // animation styles that overreach then come back)
+}
+
+
+```