Remove "theme" text from new addon-themes toolbar button

[jasosims]

Is your feature request related to a problem? Please describe.

No response

Describe the solution you'd like

The new @storybook/addon-themes addon is great! Just one request — I'd like to remove the "theme" text from the toolbar button so it only displays the name of the theme. Would be great if there's an option to hide it.

Describe alternatives you've considered

No response

Are you able to assist to bring the feature to reality?

yes, I can

Additional context

No response