make the editor resizable again

glsl/raymarching.js

  position: absolute;
  top: 0;
  left: 0;
  height: 100%;
}
#editor textarea {
  min-width: 72ex;
  height: 100vh;
  display: block;
  width: 72ex;
  height: calc(100% - 2em + 1px); /* TODO: fix this */
  resize: horizontal;
}
#editor textarea, #editor input {