How to add white border to all images in Squarespace 7.1

Hello,

What is the most straightforward way to add a 1px solid white border to all images in Squarespace 7.1?

Thanks,
Rhonda

This is code I used to handle for some sites, you can use this to Custom CSS. If it doesn't work, you can share site url, I can check again easier

.fluid-image-container, .sqs-video-wrapper {
    border: 3px double black;
}
.sqs-image, .sqs-image div {
  overflow: visible;
}
.image-block .content-fill, .image-block .content-fit, .content-fit img {
    width: calc(~"100% - 10px") !important;
    height: calc(~"100% - 10px") !important;
    top: 5px !important;
    left: 5px !important;
}
.content-fit img {
    object-fit: cover !important;
}