I think this pull request also allows moving your tests of html.rs to regression.txt after removing the trim() from the standardization function, @notriddle.

Please review the pull request to merge it, @notriddle, @mgeisler. Thanks!

This one passes.

```````````````````````````````` example
*
→ <div>
→ <div>
.
<ul>
<li>   <div>
   <div>
</li>
</ul>
````````````````````````````````

This one doesn't pass. There's an extra space before the first div. The dingus puts two spaces before both divs.

```````````````````````````````` example
*
→<div>
→<div>
.
<ul>
<li>  <div>
  <div>
</li>
</ul>
````````````````````````````````

The maximum between indent and remaining space does the trick.

Thanks a lot, @Martin1887 and @notriddle!