[FEATURE] allow to add border

[adbenitez]

Is your feature request related to a problem? Please describe.
I would like to use this library to create stickers

Describe the solution you'd like
allow to set a border_color parameter or "sticker" mode that would allow to set a white border contour

Describe alternatives you've considered
using OpenCV instead as shown in this tutorial: https://withoutbg.com/resources/creating-sticker

Additional context
the stickers are generated by a bot in a chat app and they need a white border

[github-actions]

This issue is stale because it has been open for 30 days with no activity.

[nisaji]

I will try this issue 🖐️.