Extract <h1>…</h1> title from rendered HTML and add it as <title>…</title> tag, too

[xtaran]

The returned HTML documents are full documents, but don't have a <title>…</title> tag with most formats.

It would be nice if the HTML coming from the formatting engines could be checked for (the first) <h1>…</h1> tag and their contents is then added as <title>…</title> tag, too.