Merge pull request #2813 from ZhenShuo2021/gist

✨ Feat: add CSS for gist shortcode

layouts/shortcodes/gist.html

@@ -1,3 +1,5 @@
-<script src="https://gist.github.com/{{- index .Params 0 -}}/{{- index .Params 1 -}}.js{{- if len .Params | eq 3 -}}
-    ?file={{- index .Params 2 -}}
-  {{- end -}}"></script>
+<div class="gist-container">
+  <script src="https://gist.github.com/{{- index .Params 0 -}}/{{- index .Params 1 -}}.js{{- if len .Params | eq 3 -}}
+      ?file={{- index .Params 2 -}}
+    {{- end -}}"></script>
+</div>