Atom: Put the ignored files (`.gitignore`) at the bottom of directory lists.

Atom.status-ignored_files-order.less

.list-tree {
  display: flex;
  flex-direction: column;
  flex-wrap: nowrap;
  > .status-ignored {
    // should probably be in a variable :
    order: 10;
  }
}

Atom.status-ignored_files-style.less

.directory.list-nested-item {
  > .list-tree > .file.list-item.status-ignored:not(.selected) {
    opacity: .5;
  }
  > .list-tree > .directory.list-nested-item.status-ignored:not(.selected) {
    > .header {
      opacity: .5;
    }
  }
}