Update client.mjs

Fix issue notion-enhancer#813 with the outliner extension.
Instead of inc-/dec- rementing the indentation by 18 each iteration, the fix multiplies the header level by 18. This way, jumping from level 3 to level 1 results in the correct indentation,

src/extensions/outliner/client.mjs

@@ -49,11 +49,7 @@ export default async function ({ web, components }, db) {
  const id = $header.dataset.blockId.replace(/-/g, ''),
  placeholder = $header.querySelector('[placeholder]').getAttribute('placeholder'),
  headerDepth = +[...placeholder].reverse()[0];
- if (depth && depth < headerDepth) {
- indent += 18;
- } else if (depth > headerDepth) {
- indent = Math.max(indent - 18, 0);
- }
+ indent = (headerDepth-1) * 18;
  depth = headerDepth;
  const $outlineHeader = web.render(
  web.html`<a href="#${id}" class="outliner--header"