make some API public

src/Canvas.ts

@@ -179,6 +179,5 @@ export class HitCanvas extends Canvas {
 
     this.context = new HitContext(this);
     this.setSize(config.width, config.height);
-    this.hitCanvas = true;
   }
 }

src/_CoreInternals.ts

@@ -19,7 +19,8 @@ import { Shape, shapes } from './Shape';
 import { Animation } from './Animation';
 import { Tween, Easings } from './Tween';
 
-Object.assign;
+import { Context } from './Context';
+import { Canvas } from './Canvas';
 
 export const Konva = Util._assign(Global, {
   Collection,
@@ -38,5 +39,7 @@ export const Konva = Util._assign(Global, {
   shapes,
   Animation,
   Tween,
-  Easings
+  Easings,
+  Context,
+  Canvas
 });