Reformat settings to stack Filter options / Other options vertically

[dcog989]

The options screen would make much better use of large screens if the 'Filter options' and 'Other options' were stacked vertically next to each other.

Here's a rough draft of the CSS needed to do that:

    body {
      margin: 0 auto;
      padding: 1rem;
      height: 100%;
    }

    #header,
    #main {
      margin: 0 auto;
      max-width: 1600px;
    }

    form#options {
      background-color: #eee;
      padding: 0;
      vertical-align: text-top;
    }

    form#options textarea {
      vertical-align: text-top;
    }

    .options-container {
      display: flex;
      flex-wrap: wrap;
      gap: 2rem;
      margin: 0;
      padding: 1rem;
      width: 100%;
    }

    .options-box {
      margin: 0;
      flex: 1;
      /* Distribute space evenly, min width 300px */
      min-width: 400px;
      max-width: 900px;
    }

    .options-box:nth-child(2) {
      max-width: 600px;
    }

    .buttons {
      break-before: always;
      display: block;
    }