<image><link> in RSS should link to the permalink

RSS specification says: <https://www.rssboard.org/rss-specification#ltimagegtSubelementOfLtchannelgt>

> <link> is the URL of the site, when the channel is rendered, the image is a link to the site. (Note, in practice the image <title> and <link> should have the same value as the channel's <title> and <link>.

Practically, some RSS readers may produce clicable images that leads to
homepage. Linking an image to the image itself doesn't make much sense.

layouts/_default/rss.xml

@@ -48,11 +48,11 @@
     <title>{{ if eq .Title site.Title }}{{ site.Title }}{{ else }}{{ with .Title }}{{ . }} on {{ end }}{{ site.Title }}{{ end }}</title>
     <link>{{ .Permalink }}</link>
     <description>Recent content {{ if ne .Title site.Title }}{{ with .Title }}in {{ . }} {{ end }}{{ end }}on {{ site.Title }}</description>
-    {{- with site.Params.images }}
+    {{- if site.Params.images }}
     <image>
       <title>{{ site.Title }}</title>
-      <url>{{ index . 0 | absURL }}</url>
-      <link>{{ index . 0 | absURL }}</link>
+      <url>{{ index site.Params.images 0 | absURL }}</url>
+      <link>{{ .Permalink }}</link>
     </image>
     {{- end }}
     <generator>Hugo -- {{ hugo.Version }}</generator>