add header link icon

css/tailwind.css

@@ -33,3 +33,19 @@ input:-webkit-autofill:focus {
 .katex-display {
   overflow: auto hidden;
 }
+
+.content-header-link {
+  opacity: 0;
+  margin-left: -24px;
+  padding-right: 4px;
+}
+
+.content-header:hover .content-header-link,
+.content-header-link:hover {
+  opacity: 1;
+}
+
+.linkicon {
+  display: inline-block;
+  vertical-align: middle;
+}