Spinner inside input

Created by: tkrotoff

v4.2 features spinner. They can be embedded inside a button: https://getbootstrap.com/docs/4.3/components/spinners/#buttons

Would be nice to be able to also embed a spinner inside an input.

Sometimes you have fields that perform async actions, a spinner inside the input would give feedback to the user (something is pending).

Example: https://github.com/tkrotoff/bootstrap-spinner