Engine: Add auto_close_omitted_tags option

[marcoroth]

This pull request updates the Herb::Engine to have the ability to automatically close omitted HTML closing tags when compiling and rendering templates by introducing a new auto_close_omitted_tags option.

While you are able to omit certain HTML closing tags according to the spec, it can be a bit misleading and confusing to do so. That's why Herb encourages to always close all HTML elements, even if they could be omitted.

This new auto_close_omitted_tags option now allows the templates to remain as they are, but to make sure that the rendered output of the engine is always "fully conforming" to have a closing tag in the rendered output.

For example, this template:

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

This gets compiled as:

herb compile test.html.erb --no-strict --auto-close-tags

__herb = ::Herb::Engine; _buf = ::String.new; _buf << '<ul>
  <li>List Item 1
  </li><li>List Item 2
</li></ul>
'.freeze;
_buf.to_s

And rendered as:

exe/herb render test.html.erb --no-strict --auto-close-tags

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

Builds on top of #1173

[pkg-pr-new]

npx https://pkg.pr.new/@herb-tools/formatter@1188

npx https://pkg.pr.new/@herb-tools/language-server@1188

npx https://pkg.pr.new/@herb-tools/linter@1188

commit: 315b593

[github-actions]

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_{🌱 Grown from commit 315b593}