Build the <head> discovery <link rel="alternate" type="application/rss+xml">
tag for a page, pointing feed-autodiscovery at the language-matched
feed (rss.xml for English, rss_<lang>.xml otherwise) with a
localized title.
Parameters
lang: string
Page language code
pathPrefix: string = ''
Prefix prepended to the relative feed filename
('' for root pages, '../' for pages under news/, or an absolute
${BASE_URL}/ to emit an absolute href).
Build the
<head>discovery<link rel="alternate" type="application/rss+xml">tag for a page, pointing feed-autodiscovery at the language-matched feed (rss.xmlfor English,rss_<lang>.xmlotherwise) with a localized title.