Update radio-image.md
Update radio-image.md

I have been using this docs for my field types, please correct the 'type' => 'radio' for 'type' => 'radio-image' since it does not work using only radio.

I came accross this because I was checking an issue regarding radio image not working, and it was not working for me until i found out this small change
rinkuyadav999/kirki,rinkuyadav999/kirki,rinkuyadav999/kirki,aristath/kirki,aristath/kirki,aristath/kirki,rinkuyadav999/kirki