simplify shortcode JS logic and only call AMP script if shortcodes present

fixes https://search.google.com/search-console/amp/drilldown?resource_id=sc-domain%3Ajarv.is&item_key=GgcIIhADKKZO&utm_source=wnc_10030322&utm_medium=gamma&utm_campaign=wnc_10030322&utm_content=msg_100058679&hl=en&sharing_key=VVX9zj1yTzUxHPzmKFP4Gg

layouts/shortcodes/facebook.html

@@ -4,3 +4,8 @@
 <div class="embed facebook">
 {{ $json.html | safeHTML }}
 </div>
+
+{{- define "__shortcode_facebook_js" }}
+<div id="fb-root"></div>
+<script async defer src="https://connect.facebook.net/en_US/sdk.js#xfbml=1&version=v5.0"></script>
+{{- end }}

layouts/shortcodes/gh-buttons.html

@@ -2,3 +2,7 @@
   <a class="github-button" href="https://github.com/{{ .Get "username" }}/{{ .Get "repo" }}" data-icon="octicon-star" data-size="large" data-show-count="true" aria-label="Star {{ .Get "username" }}/{{ .Get "repo" }} on GitHub">Star</a>&nbsp;&nbsp;&nbsp;
   <a class="github-button" href="https://github.com/{{ .Get "username" }}/{{ .Get "repo" }}/issues" data-icon="octicon-issue-opened" data-size="large" data-show-count="true" aria-label="Issues for {{ .Get "username" }}/{{ .Get "repo" }} on GitHub">Issue</a>
 </p></div>
+
+{{- define "__shortcode_gh-buttons_js" }}
+<script async defer src="https://buttons.github.io/buttons.js"></script>
+{{- end }}

layouts/shortcodes/instagram.amp.html

@@ -0,0 +1,7 @@
+<amp-instagram
+  data-shortcode="{{ .Get "id" }}"
+  data-captioned
+  width="500"
+  height="500"
+  layout="responsive">
+</amp-instagram>

layouts/shortcodes/instagram.html

@@ -0,0 +1,10 @@
+{{- $url := printf "https://api.instagram.com/oembed/?omitscript=1&url=https://www.instagram.com/p/%s" (.Get "id") -}}
+{{- $json := getJSON $url -}}
+
+<div class="embed instagram">
+{{ $json.html | safeHTML }}
+</div>
+
+{{- define "__shortcode_instagram_js" }}
+<script async src="https://www.instagram.com/embed.js"></script>
+{{- end }}

layouts/shortcodes/instagram.rss.xml

@@ -0,0 +1 @@
+<p style="text-align: center;"><a href="https://www.instagram.com/p/{{ .Get "id" }}" target="_blank" rel="noopener">View this image on Instagram.</a></p>

layouts/shortcodes/tweet.html

@@ -4,3 +4,7 @@
 <div class="embed tweet">
 {{ $json.html | safeHTML }}
 </div>
+
+{{- define "__shortcode_twitter_js" }}
+<script async defer src="https://platform.twitter.com/widgets.js"></script>
+{{- end }}

layouts/shortcodes/vimeo.amp.html

@@ -0,0 +1,6 @@
+<amp-vimeo
+  data-videoid="{{ .Get "id" }}"
+  layout="responsive"
+  width="500"
+  height="281">
+</amp-vimeo>

layouts/shortcodes/vimeo.html

@@ -0,0 +1,7 @@
+<div class="embed vimeo" style="padding:75% 0 0 0;position:relative;">
+  <iframe src="https://player.vimeo.com/video/{{ .Get "id" }}&amp;dnt=1" style="position:absolute;top:0;left:0;width:100%;height:100%;" frameborder="0" allow="fullscreen" allowfullscreen></iframe>
+</div>
+
+{{- define "__shortcode_vimeo_js" }}
+<script src="https://player.vimeo.com/api/player.js"></script>
+{{ end }}

layouts/shortcodes/vimeo.rss.xml

@@ -0,0 +1 @@
+<p style="text-align: center;"><a href="https://vimeo.com/{{ .Get "id" }}" target="_blank" rel="noopener">Watch this video on Vimeo.</a></p>

layouts/shortcodes/youtube.rss.xml

@@ -1 +1 @@
-<p style="text-align: center;"><a href="https://www.youtube.com/watch?v={{ index .Params 0 }}">Watch this video on YouTube.</a></p>
+<p style="text-align: center;"><a href="https://www.youtube.com/watch?v={{ index .Params 0 }}" target="_blank" rel="noopener">Watch this video on YouTube.</a></p>