message: newdoc: fixed Preview border
diff: .Preview {
  display: flex;
  align-items: flex-start;
  + position: relative;
  + border-radius: 14px;
  }
  -.Preview--vkcom .Preview__in {
  - border: none;
  +.Preview--vkcom {
  border-radius: 8px;
  }
  +.Preview::before {
  + position: absolute;
  + left: 0;
  + top: 0;
  + width: 100%;
  + height: 100%;
  + content: '';
  + border-radius: inherit;
  + box-shadow: inset 0 0 0 1px var(--image_border);
  + pointer-events: none;
  + z-index: 2;
  +}
  +
  .Preview__in {
  max-width: 100%;
  overflow: auto;
  - border: 1px solid var(--image_border);
  - border-radius: 14px;
  + border-radius: inherit;
  }
  .Preview__frame {
  