Support for fetching UI from remote configs.

[khanjasir90]

Currently, Mirai supports receiving widget json from following source.

1. Mirai.fromNetwork() -> Load data from service over a network call.
2. Mirai.fromJson() -> Mostly used for parsing purposes.
3. Mirai.fromAsset -> Load data from assets folder.

But, there can be instances where we have a json stored in remote config and we want that json to build our UI.

Adding this feature would extend the ability of Mirai to next level.

What's your thought on this @divyanshub024