It should be possible to customize .form-control:focus (border-color & box-shadow) using CSS variables.

Prerequisites

• I have searched for duplicate or closed feature requests
• I have read the contributing guidelines

Proposal

My wish is that the bootstrap team will include the option to customize .form-control:focus (border-color & box-shadow) using CSS variables.

Motivation and context

Customizing the default Bootstrap style with CSS variables is not only helpful but also easier.