Add experimental Asciinema support

layouts/_shortcodes/asciinema.html

@@ -0,0 +1,15 @@
+{{- if not (.Page.Store.Get "asciinema") -}}
+<!-- Include asciinema player only first time -->
+<link rel="stylesheet" href="{{ "asciinema/asciinema-player.css" | relURL }}" />
+<script defer src="{{ "asciinema/asciinema-player.min.js" | relURL }}"></script>
+<script defer src="{{ "asciinema/asciinema-auto.js" | relURL }}"></script>
+{{- .Page.Store.Set "asciinema" true -}}
+{{- end -}}
+
+{{- with (partial "docs/links/portable-image" (dict "Page" .Page "Destination" (index .Params "cast"))) -}}
+
+{{- $opts := newScratch -}}
+{{- $opts.Set "asciinema" $.Params -}}
+{{- $opts.DeleteInMap "asciinema" "cast" -}}
+<div class="asciinema" id="asciinema-{{ $.Ordinal }}" x-data-cast="{{ . | safeHTMLAttr }}" x-data-opts="{{ $opts.Get "asciinema" | jsonify | safeHTMLAttr }}"></div>
+{{- end -}}