Spine only renders raster images. You attach images to bones, then animate the bones. You can't render text directly, but you can make images that have the text. At runtime you could change out the images if you needed different text.
If you really wanted, you could animate just bones, then at runtime use the bones position, rotation, scale, and/or shear to render text in the right place yourself. This is probably more effort than you need to go to.