message: Rename old client_dark to space_gray scheme in docs
diff: ```css static
  :root {
  - --background_page: #141414;
  + --background_page: #ebedf0;
  }
  -body[scheme="client_dark"] {
  - --background_page: #ebedf0;
  +body[scheme="space_gray"] {
  + --background_page: #0a0a0a;
  }
  .Panel__in {
  