layouts: update RSS template to add consistent imagery

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

layouts/index.rss.xml

@@ -33,6 +33,11 @@
       {{ with .Site.Author.email }}<author>{{.}}{{ with $.Site.Author.name }} ({{.}}){{end}}</author>{{end}}
       <guid>{{ .Permalink }}</guid>
       <description>{{ .Content | html }}</description>
+      {{ if .Params.SocialImage }}
+      <image>{{ .Site.BaseURL }}{{ .Params.SocialImage }}</image>
+      {{ else }}
+      <image>{{ .Site.Params.SocialImage }}</image>
+      {{ end }}
     </item>
     {{ end }}
   </channel>