update - move to browser

[bpasero]

This enables update for web.

export interface IUpdate {
	version: string;
}

export interface IUpdateProvider {

	/**
	 * Should return with the `IUpdate` object if an update is
	 * available or `null` otherwise to signal that there are
	 * no updates.
	 */
	checkForUpdate(): Promise<IUpdate | null>;
}

Introduces a new API for web: IUpdateProvider

//cc @joaomoreno most of your code was possible to be moved to browser