give the editor small padding

glsl/raymarching.js

@@ -108,6 +108,8 @@ void main() {
  width: 72ex;
  height: calc(100% - 2em + 1px); /* TODO: fix this */
  resize: horizontal;
  padding: 1ex;
  box-sizing: border-box;
}
#editor textarea, #editor input {