🎉 Feat: add douyin shortcode support

assets/css/_shortcodes/_douyin.scss

@@ -0,0 +1,16 @@
+.douyin {
+  position: relative;
+  width: 100%;
+  height: 0;
+  padding-bottom: 60.725%;
+  margin: 3% auto;
+  text-align: center;
+
+  iframe {
+    position: absolute;
+    width: 100%;
+    height: 100%;
+    left: 0;
+    top: 0;
+  }
+}

assets/css/_shortcodes/_index.scss

@@ -1,5 +1,6 @@
 @import '_admonition';
 @import '_bilibili';
+@import '_douyin';
 @import '_cardlink';
 @import '_center-quote';
 @import '_echarts';