AutoCloseOmittedTagsVisitor

Makes sure the compiled output always contains a closing tag, even when the template omits it.

Given this template:

<ul>
  <li>List Item 1
Element `<li>` at (2:3) has its closing tag omitted. While valid HTML, consider adding an explicit `</li>` closing tag at (3:2) for clarity, or set `strict: false` to allow this. (`OMITTED_CLOSING_TAG_ERROR`) (parser-no-errors)
  <li>List Item 2
Missing explicit closing tag for `<li>`. Use `</li>` instead of relying on implicit tag closing. (html-require-closing-tags)
Element `<li>` at (3:3) has its closing tag omitted. While valid HTML, consider adding an explicit `</li>` closing tag at (4:0) for clarity, or set `strict: false` to allow this. (`OMITTED_CLOSING_TAG_ERROR`) (parser-no-errors)
</ul>
Missing explicit closing tag for `<li>`. Use `</li>` instead of relying on implicit tag closing. (html-require-closing-tags)

The engine renders:

<ul>
  <li>List Item 1
  </li><li>List Item 2
</li></ul>

The closing tag is inserted where the parser determined the element ends, which keeps the surrounding whitespace (and therefore the rendering of inline-block elements) identical to the template without the visitor.