Allow CSS theming of grid error text.

[nitroxis]

I'm customizing the styling of this (really awesome!) grid component. However, the "error" <p> appears to be hard coded currently:

Grid.Blazor/GridBlazor/Pages/GridComponent.razor

Line 89 in a9bb089

<p id="error" style="color:red;">@Error</p>

It would be very helpful if this instead used a class like .grid-error instead of element styles to allow styling of this text.

Additionally, I noticed that this element moves the grid down a bit because it is always present, no matter if it's empty or not. Wrapping it in an @if(!string.IsNullOrEmpty(Error)) { <p>... } or something similar might make sense. I managed to hide it with a CSS :empty selector for now.

[gustavnavar]

Package version 2.1.17 supports this feature.

You can override the grid-error css class or you can use another class setting the GridErrorCssClass parameter of the GridComponent object (https://github.com/gustavnavar/Grid.Blazor/blob/master/docs/blazor_server/GridBlazor_configuration.md#gridcomponent-parameters)

[nitroxis]

Cool, thanks!