How to add Image Credit for Featured Image?

In the latest update of Rishi Theme (version 1.1.5), you can now add the image credit for featured image as shown below.

To add the image credit, edit the featured image and set the caption as shown here:

Once you set the caption, navigate to Appearance > Customize > Single Post > Enable Featured Image Caption.

It also includes two layouts to choose from and customize the appearance of the caption.