Co-authored-by: Patrick Marsceill <pmarsceill@users.noreply.github.com>

Improved search documentation

This reverts commit 50cdf076.

The default is for hyphens to separate tokens in search terms: `gem-based` is equivalent to `gem based`.

This adds `search_tokenizer_separator` as a site configuation option, to support search for hyphenated words.

Because `page.title` (and `page.url`) is already escaped and page titles served by lunrjs do not need escaping, ampersands need to be unescaped to display properly in search results.

and mention `search_exclude`

The code snippet on the search documentation is missing the `relUrl` parameter in each search result, and the `url` parameter is not an absolute URL.
This updates to match the formatted output of `search.rake`