CSS for Gutenberg Support in themes

gutenberg-support.css

.has-regular-font-size {
    font-size: 16px;
}

@media only screen and (min-width: 768px) {

  .alignfull {
    margin-left: calc(50% - 50vw);
    margin-right: calc(50% - 50vw);
    width: auto;
    max-width: 1000%;
  }

  .alignwide {
    margin-left: calc(25% - 25vw);
    margin-right: calc(25% - 25vw);
    width: auto;
    max-width: 1000%;
  }

  .alignwide img,
  .alignfull img {
    display: block;
    margin: 0 auto;
  }
}