sfeed_web: a program that extracts a listing of RSS/Atom feeds from a HTML page

RSS/Atom feeds are commonly set in the <head> of a HTML file as a <link> tag.

Such a link reference in HTML looks something like:

	<link rel="alternate" href="atom.xml" type="application/atom+xml" />

To run it:

	url="https://codemadness.org/"
	curl -L -s "$url" | sfeed_web "$url"

It parses HTML from stdin and outputs a TAB-separated URL and content-type to
stdout. It has an absolute base URL command-line argument to make links into an
absolute URL if the feed url is a relative link.

Output example:

        https://codemadness.org/blog/rss.xml	application/rss+xml
        https://codemadness.org/blog/atom.xml	application/atom+xml
