Fix broken link

content/blog/sidenotes.md

@@ -10,7 +10,7 @@ I found that __sidenotes__ were a feature that I didn't even know I needed.
 A lot of my writing seems to use small parenthesized remarks (like this), which,
 although it doesn't break the flow in a grammatical sense, lengthens the
 sentence, and makes it harder to follow. Since I do my best to write content
-to help explain stuff (like the [compiler series]({{ relref "00_compiler_intro.md" }})),
+to help explain stuff (like the [compiler series]({{< relref "00_compiler_intro.md" >}})),
 making sentences __more__ difficult to understand is a no-go.
 
 So, what do they look like?

themes/vanilla/layouts/shortcodes/numberedsidenote

@@ -0,0 +1,9 @@
+{{ .Page.Scratch.Add "numbernote-id" 1 }}
+{{ $id := .Page.Scratch.Get "numbernote-id" }}
+<span class="sidenote">
+<label class="sidenote-label" for="numbernote-{{ $id }}">({{ $id }})</label>
+<input class="sidenote-checkbox" type="checkbox" id="numbernote-{{ $id }}"></input>
+<span class="sidenote-content sidenote-{{ .Get 0 }}">
+{{ .Inner }}
+</span>
+</span>