Add shortcode for audio.

layouts/shortcodes/audio.html

@@ -0,0 +1,24 @@
+{{    $src := .Get "src" | default (.Get 0)
+}} {{ $type := .Get "type"
+}} {{ if and (isset .Params "type") (not (eq $type ""))
+}}    {{ .Scratch.Set "type" $type
+}} {{ else
+}}    {{ $type := strings.TrimSuffix $src (path.Ext $src)
+}}    {{ $type := strings.TrimPrefix "." $type
+}}    {{ .Scratch.Set "type" $type
+}} {{ end
+}}
+{{ $text := .Get "text"
+}} {{ if and (isset .Params "text") (not (eq $text ""))
+}}    {{ .Scratch.Set "text" $text
+}} {{ else
+}}    {{ .Scratch.Set "text" "Audio playback is not available on your browser."
+}} {{ end
+}}
+<audio controls>
+   <source
+      src='{{ $src }}'
+      type='audio/{{ .Scratch.Get "type" }}'
+   >
+   {{ .Scratch.Get "text" }}
+</audio>