Format the html output

[eWert-Online]

Currently the html output (indentation) is not nice.

I would like to add a formatter, but it would need to respect all the html layout rules:

• content inside pre tags can't be formatted
• flow elements can be indented, but their phrasing content needs to stay as is

  <p>
    Code can appear <b>inside <code>other</code> markup</b>. Its display shouldn't be affected.
  </p>

• ... probably more