Provide an option to suppress `hx-indicator`

[hx-indicator](https://htmx.org/attributes/hx-indicator/) currently provides no way to suppress it for specific elements, e.g. to achieve showing a loading indicator by default, but don't show it for specific elements.

It would be nice if `hx-indicator="none"` or similar would be supported to not add the `htmx-request` class to a specific element. I think this is a better solution than to force the user to do the suppression via CSS, which is currently the only option.