Add automatic discovery for Atom feeds so it's easier to subscribe to new content on the site (#120)

Thank you 👍

Author: colinwilson

layouts/partials/docs/head.html

@@ -32,6 +32,10 @@
     {{ block "favicon" . }}{{ partialCached (printf "%s/%s" ($.Scratch.Get "pathName") "head/favicon.html") . }}{{ end }}
     {{- partial (printf "%s/%s" ($.Scratch.Get "pathName") "head/opengraph") . }}
     {{- partial (printf "%s/%s" ($.Scratch.Get "pathName") "head/twitter_cards") . }}
+    <!-- Atom feed autodiscovery -->
+    {{- with .Site.Title }}
+        <link rel="alternate" type="application/atom+xml" title="Atom feed for {{ . }}" href="/index.xml" />
+    {{- end }}
     <!-- Dark Mode -->
     {{ if eq .Site.Params.docs.darkMode true -}}
         {{ $darkModeInit := resources.Get (printf "/%s/%s" ($.Scratch.Get "pathName") "js/darkmode-init.js") | js.Build | minify -}}