Update Button to support IsProcessing

[StevenTCramer]

Show spinning when a particular action is being processed.

would be used like

    <Button
      Processing=@IsProcessing

where IsProcessing is calculated using something like

protected bool IsProcessing => IsProcessingAny(nameof(LoginAction));

[StevenTCramer]

Also be nice to add "Locked" status on buttons to indicate if a feature exists but is disabled, maybe it is a premium feature and user needs to upgrade.