fix: make copy button copy raw markdown

layouts/index.html

@@ -2,7 +2,7 @@
 
 {{ define "main" }}
     {{ $latest := index (where .Site.RegularPages "Section" "versions").ByDate.Reverse 0 }}
-    <div class="coc-box">
+    <div class="coc-box" data-raw-content="{{ $latest.RawContent }}">
         <button class="copy-btn" onclick="copyCoC()">[copy]</button>
         {{ $latest.Content }}
     </div>