Enhance UI performance on the async process

[wgao19]

Background:

The img.decode() is an asynchronous and potentially slow process that is required for image rasterization. This is managed by Recoil's async selector and is accessed via useRecoilValueLoadable(). This now waits for all images to be decoded and will return all of them together.

Ask:

Explore breaking down the selected values e.g. using selectorFamily such that each image can be loaded individually.

Or, explore if there are other possibilities.