add Image source imageSmoothing option

Add Image smoothing checkbox to example

Test imageSmoothing option

src/ol/source/ImageCanvas.js

@@ -36,6 +36,7 @@ import {
  * the value returned by the function is later changed then
  * `changed` should be called on the source for the source to
  * invalidate the current cached image. See: {@link module:ol/Observable~Observable#changed}
+ * @property {boolean} [imageSmoothing=true] Enable image smoothing.
  * @property {import("../proj.js").ProjectionLike} [projection] Projection. Default is the view projection.
  * @property {number} [ratio=1.5] Ratio. 1 means canvases are the size of the map viewport, 2 means twice the
  * width and height of the map viewport, and so on. Must be `1` or higher.
@@ -58,6 +59,7 @@ class ImageCanvasSource extends ImageSource {
 
     super({
       attributions: options.attributions,
+      imageSmoothing: options.imageSmoothing,
       projection: options.projection,
       resolutions: options.resolutions,
       state: options.state,