Add markup renderers

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

layouts/partials/image.html

@@ -1,10 +1,14 @@
 {{- $path := .path -}}
-{{- $alt := .alt -}}
 {{- $caption := .caption -}}
+{{- $alt := default .caption .alt -}}
 
 {{ if $path }}
   <figure class="image">
-    <img src="{{- $path | absURL -}}" {{ with $alt }}alt="{{- . -}}"{{ end }} />
+    <img
+      src="{{- $path | absURL -}}"
+      {{ with $caption }}title="{{- . -}}"{{ end }}
+      {{ with $alt }}alt="{{- . -}}"{{ end }}
+    />
     {{ with $caption }}
       <figcaption>{{ . }}</figcaption>
     {{ end }}